Bunch of fixes for GLSL display transform

- GLSL shader wasn't aware of alpha predivide option,
  always assuming alpha is straight. Gave wrong results
  when displaying transparent float buffers.

- GLSL display wasn't aware of float buffers with number
  of channels different from 4, crashing when trying to
  display image with different number of channels.

  This required a bit larger changes, namely now it's
  possible to pass format (GL_RGB, GL_RGBAm GL_LUMINANCE)
  to glaDrawPixelsTex, This also implied adding format to
  glaDrawPixelsAuto and modifying all places where this
  functions are called.

  Now GLSL will handle both 3 and 4 channels buffers,
  single channel images are handled by CPU.

- Replaced hack for render result displaying with a bit
  different hack.

  Namely CPU conversion will happen only during render,
  once render is done GLSL would be used for displaying
  render result on a screen.

  This is so because of the way renderer updates parts
  of the image -- it happens without respect to active
  render layer in image user. This is harmless because
  only display buffer is modifying, but this is tricky
  because we don't have original buffer opened during
  rendering.

  One more related fix here was about when rendering
  multiple layers, wrong image would be displaying when
  rendering is done. Added a signal to invalidate
  display buffer once rendering is done (only happens
  when using multiple layers). This solves issue with
  wrong buffer stuck on the display when using regular
  CPU display space transform and if GLSL is available
  it'll make image displayed with a GLSL shader.

- As an additional change, byte buffers now also uses
  GLSL display transform.

  So now only dutehr and RGB curves are stoppers for
  using GLSL for all kind of display transforms.

17 files changed, 235 insertions, 79 deletions

diff --git a/intern/opencolorio/fallback_impl.cc b/intern/opencolorio/fallback_impl.cc
index 4c19c454aee..37f624e1f8b 100644
--- a/intern/opencolorio/fallback_impl.cc
+++ b/intern/opencolorio/fallback_impl.cc
@@ -381,7 +381,7 @@ void FallbackImpl::matrixTransformScale(float * , float * , const float *)
 {
 }
 
-bool FallbackImpl::setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor)
+bool FallbackImpl::setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide)
 {
 	return false;
 }
diff --git a/intern/opencolorio/ocio_capi.cc b/intern/opencolorio/ocio_capi.cc
index 8e831bb0736..c8db2c2b531 100644
--- a/intern/opencolorio/ocio_capi.cc
+++ b/intern/opencolorio/ocio_capi.cc
@@ -283,9 +283,9 @@ void OCIO_matrixTransformScale(float * m44, float * offset4, const float *scale4
 	impl->matrixTransformScale(m44, offset4, scale4f);
 }
 
-int OCIO_setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor)
+int OCIO_setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, int predivide)
 {
-	return (int) impl->setupGLSLDraw(state_r, processor);
+	return (int) impl->setupGLSLDraw(state_r, processor, (bool) predivide);
 }
 
 void OCIO_finishGLSLDraw(struct OCIO_GLSLDrawState *state)
diff --git a/intern/opencolorio/ocio_capi.h b/intern/opencolorio/ocio_capi.h
index 8d8db161077..3632a0da1c6 100644
--- a/intern/opencolorio/ocio_capi.h
+++ b/intern/opencolorio/ocio_capi.h
@@ -121,7 +121,7 @@ void OCIO_matrixTransformRelease(OCIO_MatrixTransformRcPtr *mt);
 
 void OCIO_matrixTransformScale(float * m44, float * offset4, const float * scale4);
 
-int OCIO_setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor);
+int OCIO_setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, int predivide);
 void OCIO_finishGLSLDraw(struct OCIO_GLSLDrawState *state);
 void OCIO_freeOGLState(struct OCIO_GLSLDrawState *state);
 
diff --git a/intern/opencolorio/ocio_impl.h b/intern/opencolorio/ocio_impl.h
index 3a1207d0870..a328470ccb5 100644
--- a/intern/opencolorio/ocio_impl.h
+++ b/intern/opencolorio/ocio_impl.h
@@ -96,7 +96,7 @@ public:
 
 	virtual void matrixTransformScale(float * m44, float * offset4, const float * scale4) = 0;
 
-	virtual bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor) = 0;
+	virtual bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide) = 0;
 	virtual void finishGLSLDraw(struct OCIO_GLSLDrawState *state) = 0;
 	virtual void freeGLState(struct OCIO_GLSLDrawState *state_r) = 0;
 };
@@ -169,7 +169,7 @@ public:
 
 	void matrixTransformScale(float * m44, float * offset4, const float * scale4);
 
-	bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor);
+	bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide);
 	void finishGLSLDraw(struct OCIO_GLSLDrawState *state);
 	void freeGLState(struct OCIO_GLSLDrawState *state_r);
 };
@@ -243,7 +243,7 @@ public:
 
 	void matrixTransformScale(float * m44, float * offset4, const float * scale4);
 
-	bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor);
+	bool setupGLSLDraw(struct OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide);
 	void finishGLSLDraw(struct OCIO_GLSLDrawState *state);
 	void freeGLState(struct OCIO_GLSLDrawState *state_r);
 };
diff --git a/intern/opencolorio/ocio_impl_glsl.cc b/intern/opencolorio/ocio_impl_glsl.cc
index 59845abca33..9343a13e888 100644
--- a/intern/opencolorio/ocio_impl_glsl.cc
+++ b/intern/opencolorio/ocio_impl_glsl.cc
@@ -77,15 +77,33 @@ typedef struct OCIO_GLSLDrawState {
 	GLint last_texture, last_texture_unit;
 } OCIO_GLSLDrawState;
 
-static const char * g_fragShaderText = ""
+/* Hardcoded to do alpha predivide before color space conversion */
+static const char *g_fragShaderText = ""
 "\n"
 "uniform sampler2D tex1;\n"
 "uniform sampler3D tex2;\n"
+"uniform bool predivide;\n"
 "\n"
 "void main()\n"
 "{\n"
 "    vec4 col = texture2D(tex1, gl_TexCoord[0].st);\n"
-"    gl_FragColor = OCIODisplay(col, tex2);\n"
+"    if (predivide == false || col[3] == 1.0f || col[3] == 0.0f) {\n"
+"      gl_FragColor = OCIODisplay(col, tex2);\n"
+"    } else {\n"
+"      float alpha = col[3];\n"
+"      float inv_alpha = 1.0f / alpha;\n"
+"\n"
+"      col[0] *= inv_alpha;\n"
+"      col[1] *= inv_alpha;\n"
+"      col[2] *= inv_alpha;\n"
+"\n"
+"      gl_FragColor = OCIODisplay(col, tex2);\n"
+"\n"
+"      col[0] *= alpha;\n"
+"      col[1] *= alpha;\n"
+"      col[2] *= alpha;\n"
+"    }\n"
+"\n"
 "}\n";
 
 static GLuint compileShaderText(GLenum shaderType, const char *text)
@@ -187,7 +205,7 @@ static void ensureLUT3DAllocated(OCIO_GLSLDrawState *state)
  * When all drawing is finished, finishGLSLDraw shall be called to
  * restore OpenGL context to it's pre-GLSL draw state.
  */
-bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor)
+bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRcPtr *processor, bool predivide)
 {
 	ConstProcessorRcPtr ocio_processor = *(ConstProcessorRcPtr *) processor;
 
@@ -252,6 +270,7 @@ bool OCIOImpl::setupGLSLDraw(OCIO_GLSLDrawState **state_r, OCIO_ConstProcessorRc
 		glUseProgram(state->program);
 		glUniform1i(glGetUniformLocation(state->program, "tex1"), 0);
 		glUniform1i(glGetUniformLocation(state->program, "tex2"), 1);
+		glUniform1i(glGetUniformLocation(state->program, "predivide"), predivide);
 
 		return true;
 	}
diff --git a/source/blender/editors/include/BIF_glutil.h b/source/blender/editors/include/BIF_glutil.h
index a356821fb53..af2dc884508 100644
--- a/source/blender/editors/include/BIF_glutil.h
+++ b/source/blender/editors/include/BIF_glutil.h
@@ -144,17 +144,17 @@ void glaDrawPixelsSafe(float x, float y, int img_w, int img_h, int row_w, int fo
  * 1-to-1 mapping to screen space.
  */
 
-void glaDrawPixelsTex(float x, float y, int img_w, int img_h, int format, int zoomfilter, void *rect);
+void glaDrawPixelsTex(float x, float y, int img_w, int img_h, int format, int type, int zoomfilter, void *rect);
 
 /**
  * glaDrawPixelsAuto - Switches between texture or pixel drawing using UserDef.
  * only RGBA
  * needs glaDefine2DArea to be set.
  */
-void glaDrawPixelsAuto(float x, float y, int img_w, int img_h, int format, int zoomfilter, void *rect);
+void glaDrawPixelsAuto(float x, float y, int img_w, int img_h, int format, int type, int zoomfilter, void *rect);
 
 
-void glaDrawPixelsTexScaled(float x, float y, int img_w, int img_h, int format, int zoomfilter, void *rect, float scaleX, float scaleY);
+void glaDrawPixelsTexScaled(float x, float y, int img_w, int img_h, int format, int type, int zoomfilter, void *rect, float scaleX, float scaleY);
 
 /* 2D Drawing Assistance */
 
diff --git a/source/blender/editors/interface/interface_draw.c b/source/blender/editors/interface/interface_draw.c
index 6edbb90febe..c0f1ed28b3f 100644
--- a/source/blender/editors/interface/interface_draw.c
+++ b/source/blender/editors/interface/interface_draw.c
@@ -454,7 +454,7 @@ void ui_draw_but_IMAGE(ARegion *UNUSED(ar), uiBut *but, uiWidgetColors *UNUSED(w
 		float facy = (float)h / (float)ibuf->y;
 		glPixelZoom(facx, facy);
 	}
-	glaDrawPixelsAuto((float)rect->xmin, (float)rect->ymin, ibuf->x, ibuf->y, GL_UNSIGNED_BYTE, GL_NEAREST, ibuf->rect);
+	glaDrawPixelsAuto((float)rect->xmin, (float)rect->ymin, ibuf->x, ibuf->y, GL_RGBA, GL_UNSIGNED_BYTE, GL_NEAREST, ibuf->rect);
 	
 	glPixelZoom(1.0f, 1.0f);
 	
diff --git a/source/blender/editors/render/render_internal.c b/source/blender/editors/render/render_internal.c
index 90c80cae1ad..6832cd5baa0 100644
--- a/source/blender/editors/render/render_internal.c
+++ b/source/blender/editors/render/render_internal.c
@@ -429,10 +429,38 @@ static void render_endjob(void *rjv)
 		nodeUpdateID(rj->scene->nodetree, &rj->scene->id);
 		WM_main_add_notifier(NC_NODE | NA_EDITED, rj->scene);
 	}
-	
+
 	/* XXX render stability hack */
 	G.is_rendering = FALSE;
 	WM_main_add_notifier(NC_WINDOW, NULL);
+
+	/* Partial render result will always update display buffer
+	 * for first render layer only. This is nice because you'll
+	 * see render progress during rendering, but it ends up in
+	 * wrong display buffer shown after rendering.
+	 *
+	 * The code below will mark display buffer as invalid after
+	 * rendering in case multiple layers were rendered, which
+	 * ensures display buffer matches render layer after
+	 * rendering.
+	 *
+	 * Perhaps proper way would be to toggle active render
+	 * layer in image editor and job, so we always display
+	 * layer being currently rendered. But this is not so much
+	 * trivial at this moment, especially because of external
+	 * engine API, so lets use simple and robust way for now
+	 *                                          - sergey -
+	 */
+	if (rj->scene->r.layers.first != rj->scene->r.layers.last) {
+		void *lock;
+		Image *ima = rj->image;
+		ImBuf *ibuf = BKE_image_acquire_ibuf(ima, &rj->iuser, &lock);
+
+		if (ibuf)
+			ibuf->userflags |= IB_DISPLAY_BUFFER_INVALID;
+
+		BKE_image_release_ibuf(ima, ibuf, lock);
+	}
 }
 
 /* called by render, check job 'stop' value or the global */
diff --git a/source/blender/editors/screen/glutil.c b/source/blender/editors/screen/glutil.c
index b5c2b106a15..ec1a085f9da 100644
--- a/source/blender/editors/screen/glutil.c
+++ b/source/blender/editors/screen/glutil.c
@@ -42,6 +42,7 @@
 #include "BLI_threads.h"
 
 #include "BKE_blender.h"
+#include "BKE_global.h"
 #include "BKE_colortools.h"
 #include "BKE_context.h"
 
@@ -488,7 +489,7 @@ static int get_cached_work_texture(int *w_r, int *h_r)
 	return texid;
 }
 
-void glaDrawPixelsTexScaled(float x, float y, int img_w, int img_h, int format, int zoomfilter, void *rect, float scaleX, float scaleY)
+void glaDrawPixelsTexScaled(float x, float y, int img_w, int img_h, int format, int type, int zoomfilter, void *rect, float scaleX, float scaleY)
 {
 	unsigned char *uc_rect = (unsigned char *) rect;
 	float *f_rect = (float *)rect;
@@ -498,7 +499,8 @@ void glaDrawPixelsTexScaled(float x, float y, int img_w, int img_h, int format,
 	int subpart_x, subpart_y, tex_w, tex_h;
 	int seamless, offset_x, offset_y, nsubparts_x, nsubparts_y;
 	int texid = get_cached_work_texture(&tex_w, &tex_h);
-	
+	int components;
+
 	/* Specify the color outside this function, and tex will modulate it.
 	 * This is useful for changing alpha without using glPixelTransferf()
 	 */
@@ -525,13 +527,22 @@ void glaDrawPixelsTexScaled(float x, float y, int img_w, int img_h, int format,
 	nsubparts_x = (img_w + (offset_x - 1)) / (offset_x);
 	nsubparts_y = (img_h + (offset_y - 1)) / (offset_y);
 
-	if (format == GL_FLOAT) {
+	if (format == GL_RGBA)
+		components = 4;
+	else if (format == GL_RGB)
+		components = 3;
+	else if (format == GL_LUMINANCE)
+		components = 1;
+	else
+		BLI_assert(!"Incompatible format passed to glaDrawPixelsTexScaled");
+
+	if (type == GL_FLOAT) {
 		/* need to set internal format to higher range float */
-		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, tex_w, tex_h, 0, GL_RGBA, GL_FLOAT, NULL);
+		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F_ARB, tex_w, tex_h, 0, format, GL_FLOAT, NULL);
 	}
 	else {
 		/* switch to 8bit RGBA for byte buffer  */
-		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, tex_w, tex_h, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, tex_w, tex_h, 0, format, GL_UNSIGNED_BYTE, NULL);
 	}
 
 	for (subpart_y = 0; subpart_y < nsubparts_y; subpart_y++) {
@@ -551,26 +562,26 @@ void glaDrawPixelsTexScaled(float x, float y, int img_w, int img_h, int format,
 			if (subpart_w <= seamless || subpart_h <= seamless)
 				continue;
 			
-			if (format == GL_FLOAT) {
-				glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, subpart_w, subpart_h, GL_RGBA, GL_FLOAT, &f_rect[subpart_y * offset_y * img_w * 4 + subpart_x * offset_x * 4]);
+			if (type == GL_FLOAT) {
+				glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, subpart_w, subpart_h, format, GL_FLOAT, &f_rect[subpart_y * offset_y * img_w * components + subpart_x * offset_x * components]);
 				
 				/* add an extra border of pixels so linear looks ok at edges of full image. */
 				if (subpart_w < tex_w)
-					glTexSubImage2D(GL_TEXTURE_2D, 0, subpart_w, 0, 1, subpart_h, GL_RGBA, GL_FLOAT, &f_rect[subpart_y * offset_y * img_w * 4 + (subpart_x * offset_x + subpart_w - 1) * 4]);
+					glTexSubImage2D(GL_TEXTURE_2D, 0, subpart_w, 0, 1, subpart_h, format, GL_FLOAT, &f_rect[subpart_y * offset_y * img_w * components + (subpart_x * offset_x + subpart_w - 1) * components]);
 				if (subpart_h < tex_h)
-					glTexSubImage2D(GL_TEXTURE_2D, 0, 0, subpart_h, subpart_w, 1, GL_RGBA, GL_FLOAT, &f_rect[(subpart_y * offset_y + subpart_h - 1) * img_w * 4 + subpart_x * offset_x * 4]);
+					glTexSubImage2D(GL_TEXTURE_2D, 0, 0, subpart_h, subpart_w, 1, format, GL_FLOAT, &f_rect[(subpart_y * offset_y + subpart_h - 1) * img_w * components + subpart_x * offset_x * components]);
 				if (subpart_w < tex_w && subpart_h < tex_h)
-					glTexSubImage2D(GL_TEXTURE_2D, 0, subpart_w, subpart_h, 1, 1, GL_RGBA, GL_FLOAT, &f_rect[(subpart_y * offset_y + subpart_h - 1) * img_w * 4 + (subpart_x * offset_x + subpart_w - 1) * 4]);
+					glTexSubImage2D(GL_TEXTURE_2D, 0, subpart_w, subpart_h, 1, 1, format, GL_FLOAT, &f_rect[(subpart_y * offset_y + subpart_h - 1) * img_w * components + (subpart_x * offset_x + subpart_w - 1) * components]);
 			}
 			else {
-				glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, subpart_w, subpart_h, GL_RGBA, GL_UNSIGNED_BYTE, &uc_rect[subpart_y * offset_y * img_w * 4 + subpart_x * offset_x * 4]);
+				glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, subpart_w, subpart_h, format, GL_UNSIGNED_BYTE, &uc_rect[subpart_y * offset_y * img_w * components + subpart_x * offset_x * components]);
 				
 				if (subpart_w < tex_w)
-					glTexSubImage2D(GL_TEXTURE_2D, 0, subpart_w, 0, 1, subpart_h, GL_RGBA, GL_UNSIGNED_BYTE, &uc_rect[subpart_y * offset_y * img_w * 4 + (subpart_x * offset_x + subpart_w - 1) * 4]);
+					glTexSubImage2D(GL_TEXTURE_2D, 0, subpart_w, 0, 1, subpart_h, format, GL_UNSIGNED_BYTE, &uc_rect[subpart_y * offset_y * img_w * components + (subpart_x * offset_x + subpart_w - 1) * components]);
 				if (subpart_h < tex_h)
-					glTexSubImage2D(GL_TEXTURE_2D, 0, 0, subpart_h, subpart_w, 1, GL_RGBA, GL_UNSIGNED_BYTE, &uc_rect[(subpart_y * offset_y + subpart_h - 1) * img_w * 4 + subpart_x * offset_x * 4]);
+					glTexSubImage2D(GL_TEXTURE_2D, 0, 0, subpart_h, subpart_w, 1, format, GL_UNSIGNED_BYTE, &uc_rect[(subpart_y * offset_y + subpart_h - 1) * img_w * components + subpart_x * offset_x * components]);
 				if (subpart_w < tex_w && subpart_h < tex_h)
-					glTexSubImage2D(GL_TEXTURE_2D, 0, subpart_w, subpart_h, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, &uc_rect[(subpart_y * offset_y + subpart_h - 1) * img_w * 4 + (subpart_x * offset_x + subpart_w - 1) * 4]);
+					glTexSubImage2D(GL_TEXTURE_2D, 0, subpart_w, subpart_h, 1, 1, format, GL_UNSIGNED_BYTE, &uc_rect[(subpart_y * offset_y + subpart_h - 1) * img_w * components + (subpart_x * offset_x + subpart_w - 1) * components]);
 			}
 
 			glEnable(GL_TEXTURE_2D);
@@ -601,9 +612,9 @@ void glaDrawPixelsTexScaled(float x, float y, int img_w, int img_h, int format,
 #endif
 }
 
-void glaDrawPixelsTex(float x, float y, int img_w, int img_h, int format, int zoomfilter, void *rect)
+void glaDrawPixelsTex(float x, float y, int img_w, int img_h, int format, int type, int zoomfilter, void *rect)
 {
-	glaDrawPixelsTexScaled(x, y, img_w, img_h, format, zoomfilter, rect, 1.0f, 1.0f);
+	glaDrawPixelsTexScaled(x, y, img_w, img_h, format, type, zoomfilter, rect, 1.0f, 1.0f);
 }
 
 void glaDrawPixelsSafe(float x, float y, int img_w, int img_h, int row_w, int format, int type, void *rect)
@@ -686,7 +697,7 @@ void glaDrawPixelsSafe(float x, float y, int img_w, int img_h, int row_w, int fo
 }
 
 /* uses either DrawPixelsSafe or DrawPixelsTex, based on user defined maximum */
-void glaDrawPixelsAuto(float x, float y, int img_w, int img_h, int format, int zoomfilter, void *rect)
+void glaDrawPixelsAuto(float x, float y, int img_w, int img_h, int format, int type, int zoomfilter, void *rect)
 {
 	if (U.image_gpubuffer_limit) {
 		/* Megapixels, use float math to prevent overflow */
@@ -694,11 +705,11 @@ void glaDrawPixelsAuto(float x, float y, int img_w, int img_h, int format, int z
 		
 		if (U.image_gpubuffer_limit > (int)img_size) {
 			glColor4f(1.0, 1.0, 1.0, 1.0);
-			glaDrawPixelsTex(x, y, img_w, img_h, format, zoomfilter, rect);
+			glaDrawPixelsTex(x, y, img_w, img_h, format, type, zoomfilter, rect);
 			return;
 		}
 	}
-	glaDrawPixelsSafe(x, y, img_w, img_h, img_w, GL_RGBA, format, rect);
+	glaDrawPixelsSafe(x, y, img_w, img_h, img_w, format, type, rect);
 }
 
 /* 2D Drawing Assistance */
@@ -1017,22 +1028,83 @@ void bglFlush(void)
 /* Draw given image buffer on a screen using GLSL for display transform */
 void glaDrawImBuf_glsl_ctx(const bContext *C, ImBuf *ibuf, float x, float y, int zoomfilter)
 {
+	bool force_fallback = false;
 	bool need_fallback = true;
 
-	/* Bytes and dithering are not supported on GLSL yet */
+	/* Early out */
+	if (ibuf->rect == NULL && ibuf->rect_float == NULL)
+		return;
+
+	/* Dithering is not supported on GLSL yet */
+	force_fallback = ibuf->dither != 0.0f;
+
+	/* Single channel images could not be transformed using GLSL yet */
+	force_fallback = ibuf->channels == 1;
 
-	/* WORKAROUND: only use GLSL if there's no byte buffer at all,
-	 *             this is because of how render results are handled,
-	 *             they're not updating image buffer's float buffer,
-	 *             but writes data directly to it's byte buffer and
-	 *             modifies display buffer.
+	/* This is actually lots of crap, but currently not sure about
+	 * more clear way to bypass partial buffer update crappyness
+	 * while rendering.
+	 *
+	 * The thing is -- render engines are only updating byte and
+	 * display buffers for active render result opened in image
+	 * editor. This works fine to show render progress without
+	 * switching render layers in image editor user, but this is
+	 * completely useless for GLSL display, where we need to have
+	 * original buffer which we could color manage.
+	 *
+	 * For the time of rendering, we'll stick back to slower CPU
+	 * display buffer update. GLSL could be used as soon as some
+	 * fixes (?) are done in render itself, so we'll always have
+	 * image buffer with relevant float buffer opened while
+	 * rendering.
+	 *
+	 * On the other hand, when using Cycles, stressing GPU with
+	 * GLSL could backfire on a performance.
+	 *                                         - sergey -
 	 */
-	if (ibuf->rect == NULL && ibuf->rect_float && ibuf->dither == 0.0f) {
-		if (IMB_colormanagement_setup_glsl_draw_from_ctx(C)) {
+	if (G.is_rendering) {
+		/* Try to detect whether we're drawing render result,
+		 * other images could have both rect and rect_float
+		 * but they'll be synchronized
+		 */
+		if (ibuf->rect_float && ibuf->rect &&
+		    ((ibuf->mall & IB_rectfloat) == 0))
+		{
+			force_fallback = true;
+		}
+	}
+
+	/* Try to draw buffer using GLSL display transform */
+	if (force_fallback == false) {
+		int ok;
+
+		if (ibuf->rect_float)
+			ok = IMB_colormanagement_setup_glsl_draw_ctx(C, TRUE);
+		else
+			ok = IMB_colormanagement_setup_glsl_draw_from_space_ctx(C, ibuf->rect_colorspace, FALSE);
+
+		if (ok) {
 			glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
 			glColor4f(1.0, 1.0, 1.0, 1.0);
 
-			glaDrawPixelsTex(x, y, ibuf->x, ibuf->y, GL_FLOAT, zoomfilter, ibuf->rect_float);
+			if (ibuf->rect_float) {
+				int format;
+
+				if (ibuf->channels == 3)
+					format = GL_RGB;
+				else if (ibuf->channels == 4)
+					format = GL_RGBA;
+				else
+					BLI_assert(!"Incompatible number of channels for GLSL display");
+
+				glaDrawPixelsTex(x, y, ibuf->x, ibuf->y, format, GL_FLOAT,
+				                 zoomfilter, ibuf->rect_float);
+			}
+			else if (ibuf->rect) {
+				/* ibuf->rect is always RGBA */
+				glaDrawPixelsTex(x, y, ibuf->x, ibuf->y, GL_RGBA, GL_UNSIGNED_BYTE,
+				                 zoomfilter, ibuf->rect);
+			}
 
 			IMB_colormanagement_finish_glsl_draw();
 
@@ -1040,6 +1112,7 @@ void glaDrawImBuf_glsl_ctx(const bContext *C, ImBuf *ibuf, float x, float y, int
 		}
 	}
 
+	/* In case GLSL failed or not usable, fallback to glaDrawPixelsAuto */
 	if (need_fallback) {
 		unsigned char *display_buffer;
 		void *cache_handle;
@@ -1047,7 +1120,8 @@ void glaDrawImBuf_glsl_ctx(const bContext *C, ImBuf *ibuf, float x, float y, int
 		display_buffer = IMB_display_buffer_acquire_ctx(C, ibuf, &cache_handle);
 
 		if (display_buffer)
-			glaDrawPixelsAuto(x, y, ibuf->x, ibuf->y, GL_UNSIGNED_BYTE, zoomfilter, display_buffer);
+			glaDrawPixelsAuto(x, y, ibuf->x, ibuf->y, GL_RGBA, GL_UNSIGNED_BYTE,
+			                  zoomfilter, display_buffer);
 
 		IMB_display_buffer_release(cache_handle);
 	}
@@ -1057,6 +1131,8 @@ void glaDrawImBuf_glsl_ctx(const bContext *C, ImBuf *ibuf, float x, float y, int
  *
  * See IMB_colormanagement_setup_transform_from_role_glsl description for
  * some more details
+ *
+ * NOTE: this only works for RGBA buffers!
  */
 int glaBufferTransformFromRole_glsl(float *buffer, int width, int height, int role)
 {
@@ -1071,7 +1147,7 @@ int glaBufferTransformFromRole_glsl(float *buffer, int width, int height, int ro
 
 	GPU_offscreen_bind(ofs);
 
-	if (!IMB_colormanagement_setup_transform_from_role_glsl(role)) {
+	if (!IMB_colormanagement_setup_transform_from_role_glsl(role, TRUE)) {
 		GPU_offscreen_unbind(ofs);
 		GPU_offscreen_free(ofs);
 		return FALSE;
@@ -1085,9 +1161,9 @@ int glaBufferTransformFromRole_glsl(float *buffer, int width, int height, int ro
 	glPushMatrix();
 
 	glaDefine2DArea(&display_rect);
-	glLoadIdentity();
 
-	glaDrawPixelsTex(0, 0, width, height, GL_FLOAT, GL_NEAREST, buffer);
+	glaDrawPixelsTex(0, 0, width, height, GL_RGBA, GL_FLOAT,
+	                 GL_NEAREST, buffer);
 
 	glMatrixMode(GL_PROJECTION);
 	glPopMatrix();
diff --git a/source/blender/editors/space_file/file_draw.c b/source/blender/editors/space_file/file_draw.c
index 1c677d7c006..601c86b3029 100644
--- a/source/blender/editors/space_file/file_draw.c
+++ b/source/blender/editors/space_file/file_draw.c
@@ -376,7 +376,7 @@ static void file_draw_preview(uiBlock *block, struct direntry *file, int sx, int
 		
 		/* the image */
 		glColor4f(1.0, 1.0, 1.0, 1.0);
-		glaDrawPixelsTexScaled((float)xco, (float)yco, imb->x, imb->y, GL_UNSIGNED_BYTE, GL_NEAREST, imb->rect, scale, scale);
+		glaDrawPixelsTexScaled((float)xco, (float)yco, imb->x, imb->y, GL_RGBA, GL_UNSIGNED_BYTE, GL_NEAREST, imb->rect, scale, scale);
 		
 		/* border */
 		if (dropshadow) {
diff --git a/source/blender/editors/space_node/drawnode.c b/source/blender/editors/space_node/drawnode.c
index 5e5b2ece8c9..d7206c9b111 100644
--- a/source/blender/editors/space_node/drawnode.c
+++ b/source/blender/editors/space_node/drawnode.c
@@ -3011,7 +3011,7 @@ void draw_nodespace_back_pix(const bContext *C, ARegion *ar, SpaceNode *snode)
 					glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 					glPixelZoom(snode->zoom, snode->zoom);
 					
-					glaDrawPixelsAuto(x, y, ibuf->x, ibuf->y, GL_UNSIGNED_BYTE, GL_NEAREST, display_buffer);
+					glaDrawPixelsAuto(x, y, ibuf->x, ibuf->y, GL_RGBA, GL_UNSIGNED_BYTE, GL_NEAREST, display_buffer);
 					
 					glPixelZoom(1.0f, 1.0f);
 					glDisable(GL_BLEND);
@@ -3019,7 +3019,7 @@ void draw_nodespace_back_pix(const bContext *C, ARegion *ar, SpaceNode *snode)
 				else {
 					glPixelZoom(snode->zoom, snode->zoom);
 
-					glaDrawPixelsAuto(x, y, ibuf->x, ibuf->y, GL_UNSIGNED_BYTE, GL_NEAREST, display_buffer);
+					glaDrawPixelsAuto(x, y, ibuf->x, ibuf->y, GL_RGBA, GL_UNSIGNED_BYTE, GL_NEAREST, display_buffer);
 					
 					glPixelZoom(1.0f, 1.0f);
 				}
diff --git a/source/blender/editors/space_node/node_draw.c b/source/blender/editors/space_node/node_draw.c
index f1915a82f69..39b12b321dd 100644
--- a/source/blender/editors/space_node/node_draw.c
+++ b/source/blender/editors/space_node/node_draw.c
@@ -710,7 +710,7 @@ static void node_draw_preview(bNodePreview *preview, rctf *prv)
 	
 	glColor4f(1.0, 1.0, 1.0, 1.0);
 	glPixelZoom(scale, scale);
-	glaDrawPixelsTex(draw_rect.xmin, draw_rect.ymin, preview->xsize, preview->ysize, GL_UNSIGNED_BYTE, GL_LINEAR, preview->rect);
+	glaDrawPixelsTex(draw_rect.xmin, draw_rect.ymin, preview->xsize, preview->ysize, GL_RGBA, GL_UNSIGNED_BYTE, GL_LINEAR, preview->rect);
 	glPixelZoom(1.0f, 1.0f);
 	
 	glDisable(GL_BLEND);
diff --git a/source/blender/editors/space_view3d/drawobject.c b/source/blender/editors/space_view3d/drawobject.c
index 2f0a2b7cb7a..6a450f6415e 100644
--- a/source/blender/editors/space_view3d/drawobject.c
+++ b/source/blender/editors/space_view3d/drawobject.c
@@ -618,7 +618,7 @@ static void draw_empty_image(Object *ob, const short dflag, const unsigned char
 		glColor4fv(ob->col);
 
 		/* Draw the Image on the screen */
-		glaDrawPixelsTex(ofs_x, ofs_y, ima_x, ima_y, GL_UNSIGNED_BYTE, GL_LINEAR, ibuf->rect);
+		glaDrawPixelsTex(ofs_x, ofs_y, ima_x, ima_y, GL_RGBA, GL_UNSIGNED_BYTE, GL_LINEAR, ibuf->rect);
 		glPixelTransferf(GL_ALPHA_SCALE, 1.0f);
 
 		glDisable(GL_BLEND);
diff --git a/source/blender/editors/space_view3d/view3d_draw.c b/source/blender/editors/space_view3d/view3d_draw.c
index b6d46f82e6a..d0437c77af7 100644
--- a/source/blender/editors/space_view3d/view3d_draw.c
+++ b/source/blender/editors/space_view3d/view3d_draw.c
@@ -1831,7 +1831,7 @@ static void view3d_draw_bgpic(Scene *scene, ARegion *ar, View3D *v3d,
 			 * glaDrawPixelsSafe in some cases, which will end up in misssing
 			 * alpha transparency for the background image (sergey)
 			 */
-			glaDrawPixelsTex(x1, y1, ibuf->x, ibuf->y, GL_UNSIGNED_BYTE, GL_LINEAR, ibuf->rect);
+			glaDrawPixelsTex(x1, y1, ibuf->x, ibuf->y, GL_RGBA, GL_UNSIGNED_BYTE, GL_LINEAR, ibuf->rect);
 
 			glPixelZoom(1.0, 1.0);
 			glPixelTransferf(GL_ALPHA_SCALE, 1.0f);
diff --git a/source/blender/imbuf/IMB_colormanagement.h b/source/blender/imbuf/IMB_colormanagement.h
index a758cfa04f0..203d01cab67 100644
--- a/source/blender/imbuf/IMB_colormanagement.h
+++ b/source/blender/imbuf/IMB_colormanagement.h
@@ -152,14 +152,22 @@ void IMB_colormanagement_processor_free(struct ColormanageProcessor *cm_processo
 
 /* Configures GLSL shader for conversion from scene linear to display space */
 int IMB_colormanagement_setup_glsl_draw(const struct ColorManagedViewSettings *view_settings,
-                                        const struct ColorManagedDisplaySettings *display_settings);
-/* Same as above, but color management settings are guessing from a given context */
-int IMB_colormanagement_setup_glsl_draw_from_ctx(const struct bContext *C);
+                                        const struct ColorManagedDisplaySettings *display_settings,
+                                        int predivide);
+/* Same as above, but display space conversion happens from a specified space */
+int IMB_colormanagement_setup_glsl_draw_from_space(const struct ColorManagedViewSettings *view_settings,
+                                                   const struct ColorManagedDisplaySettings *display_settings,
+                                                   struct ColorSpace *colorspace,
+                                                   int predivide);
+/* Same as setup_glsl_draw, but color management settings are guessing from a given context */
+int IMB_colormanagement_setup_glsl_draw_ctx(const struct bContext *C, int predivide);
+/* Same as setup_glsl_draw_from_space, but color management settings are guessing from a given context */
+int IMB_colormanagement_setup_glsl_draw_from_space_ctx(const struct bContext *C, struct ColorSpace *colorspace, int predivide);
 /* Finish GLSL-based display space conversion */
 void IMB_colormanagement_finish_glsl_draw(void);
 
 /* Configures GLSL shader for conversion from space defined by role to scene linear space */
-int IMB_colormanagement_setup_transform_from_role_glsl(int role);
+int IMB_colormanagement_setup_transform_from_role_glsl(int role, int predivide);
 /* Finish GLSL-based color space conversion */
 void IMB_colormanagement_finish_glsl_transform(void);
 
diff --git a/source/blender/imbuf/intern/colormanagement.c b/source/blender/imbuf/intern/colormanagement.c
index 3ed69550873..1e6fac4f4f0 100644
--- a/source/blender/imbuf/intern/colormanagement.c
+++ b/source/blender/imbuf/intern/colormanagement.c
@@ -109,6 +109,7 @@ static struct global_glsl_state {
 	/* Settings of processor for comparison. */
 	char view[MAX_COLORSPACE_NAME];
 	char display[MAX_COLORSPACE_NAME];
+	char input[MAX_COLORSPACE_NAME];
 	float exposure, gamma;
 
 	/* Container for GLSL state needed for OCIO module. */
@@ -703,8 +704,10 @@ static ColorSpace *display_transform_get_colorspace(const ColorManagedViewSettin
 	return NULL;
 }
 
-static OCIO_ConstProcessorRcPtr *create_display_buffer_processor(const char *view_transform, const char *display,
-                                                                 float exposure, float gamma)
+static OCIO_ConstProcessorRcPtr *create_display_buffer_processor(const char *view_transform,
+                                                                 const char *display,
+                                                                 float exposure, float gamma,
+                                                                 const char *from_colorspace)
 {
 	OCIO_ConstConfigRcPtr *config = OCIO_getCurrentConfig();
 	OCIO_DisplayTransformRcPtr *dt;
@@ -712,8 +715,7 @@ static OCIO_ConstProcessorRcPtr *create_display_buffer_processor(const char *vie
 
 	dt = OCIO_createDisplayTransform();
 
-	/* assuming handling buffer was already converted to scene linear space */
-	OCIO_displayTransformSetInputColorSpaceName(dt, global_role_scene_linear);
+	OCIO_displayTransformSetInputColorSpaceName(dt, from_colorspace);
 	OCIO_displayTransformSetView(dt, view_transform);
 	OCIO_displayTransformSetDisplay(dt, display);
 
@@ -2621,7 +2623,8 @@ ColormanageProcessor *IMB_colormanagement_display_processor_new(const ColorManag
 		cm_processor->is_data_result = display_space->is_data;
 
 	cm_processor->processor = create_display_buffer_processor(applied_view_settings->view_transform, display_settings->display_device,
-	                                                          applied_view_settings->exposure, applied_view_settings->gamma);
+	                                                          applied_view_settings->exposure, applied_view_settings->gamma,
+	                                                          global_role_scene_linear);
 
 	if (applied_view_settings->flag & COLORMANAGE_VIEW_USE_CURVES) {
 		cm_processor->curve_mapping = curvemapping_copy(applied_view_settings->curve_mapping);
@@ -2718,26 +2721,30 @@ void IMB_colormanagement_processor_free(ColormanageProcessor *cm_processor)
 /* **** OpenGL drawing routines using GLSL for color space transform ***** */
 
 static bool check_glsl_display_processor_changed(const ColorManagedViewSettings *view_settings,
-                                                 const ColorManagedDisplaySettings *display_settings)
+                                                 const ColorManagedDisplaySettings *display_settings,
+                                                 const char *from_colorspace)
 {
 	return !(global_glsl_state.exposure == view_settings->exposure &&
 	         global_glsl_state.gamma == view_settings->gamma &&
 	         STREQ(global_glsl_state.view, view_settings->view_transform) &&
-	         STREQ(global_glsl_state.display, display_settings->display_device));
+	         STREQ(global_glsl_state.display, display_settings->display_device) &&
+	         STREQ(global_glsl_state.input, from_colorspace));
 }
 
 static void update_glsl_display_processor(const ColorManagedViewSettings *view_settings,
-                                          const ColorManagedDisplaySettings *display_settings)
+                                          const ColorManagedDisplaySettings *display_settings,
+                                          const char *from_colorspace)
 {
 	/* Update state if there's no processor yet or
 	 * processor settings has been changed.
 	 */
 	if (global_glsl_state.processor == NULL ||
-	    check_glsl_display_processor_changed(view_settings, display_settings))
+	    check_glsl_display_processor_changed(view_settings, display_settings, from_colorspace))
 	{
 		/* Store settings of processor for further comparison. */
 		strcpy(global_glsl_state.view, view_settings->view_transform);
 		strcpy(global_glsl_state.display, display_settings->display_device);
+		strcpy(global_glsl_state.input, from_colorspace);
 		global_glsl_state.exposure = view_settings->exposure;
 		global_glsl_state.gamma = view_settings->gamma;
 
@@ -2750,13 +2757,14 @@ static void update_glsl_display_processor(const ColorManagedViewSettings *view_s
 			create_display_buffer_processor(global_glsl_state.view,
 			                                global_glsl_state.display,
 			                                global_glsl_state.exposure,
-			                                global_glsl_state.gamma);
+			                                global_glsl_state.gamma,
+			                                global_glsl_state.input);
 	}
 }
 
 /**
- * Configures GLSL shader for conversion from scene linear
- * to display space
+ * Configures GLSL shader for conversion from specified to
+ * display color space
  *
  * Will create appropriate OCIO processor and setup GLSL shader,
  * so further 2D texture usage will use this conversion.
@@ -2767,8 +2775,9 @@ static void update_glsl_display_processor(const ColorManagedViewSettings *view_s
  * This is low-level function, use glaDrawImBuf_glsl_ctx if you
  * only need to display given image buffer
  */
-int IMB_colormanagement_setup_glsl_draw(const ColorManagedViewSettings *view_settings,
-                                        const ColorManagedDisplaySettings *display_settings)
+int IMB_colormanagement_setup_glsl_draw_from_space(const ColorManagedViewSettings *view_settings,
+                                                   const ColorManagedDisplaySettings *display_settings,
+                                                   struct ColorSpace *from_colorspace, int predivide)
 {
 	ColorManagedViewSettings default_view_settings;
 	const ColorManagedViewSettings *applied_view_settings;
@@ -2790,20 +2799,36 @@ int IMB_colormanagement_setup_glsl_draw(const ColorManagedViewSettings *view_set
 		return FALSE;
 
 	/* Make sure OCIO processor is up-to-date. */
-	update_glsl_display_processor(applied_view_settings, display_settings);
+	update_glsl_display_processor(applied_view_settings, display_settings,
+	                              from_colorspace ? from_colorspace->name : global_role_scene_linear);
+
+	return OCIO_setupGLSLDraw(&global_glsl_state.ocio_glsl_state, global_glsl_state.processor, predivide);
+}
 
-	return OCIO_setupGLSLDraw(&global_glsl_state.ocio_glsl_state, global_glsl_state.processor);
+/* Configures GLSL shader for conversion from scene linear to display space */
+int IMB_colormanagement_setup_glsl_draw(const ColorManagedViewSettings *view_settings,
+                                        const ColorManagedDisplaySettings *display_settings,
+										int predivide)
+{
+	return IMB_colormanagement_setup_glsl_draw_from_space(view_settings, display_settings,
+	                                                      NULL, predivide);
 }
 
-/* Same as above, but color management settings are guessing from a given context */
-int IMB_colormanagement_setup_glsl_draw_from_ctx(const bContext *C)
+/* Same as setup_glsl_draw_from_space, but color management settings are guessing from a given context */
+int IMB_colormanagement_setup_glsl_draw_from_space_ctx(const struct bContext *C, struct ColorSpace *from_colorspace, int predivide)
 {
 	ColorManagedViewSettings *view_settings;
 	ColorManagedDisplaySettings *display_settings;
 
 	display_transform_get_from_ctx(C, &view_settings, &display_settings);
 
-	return IMB_colormanagement_setup_glsl_draw(view_settings, display_settings);
+	return IMB_colormanagement_setup_glsl_draw_from_space(view_settings, display_settings, from_colorspace, predivide);
+}
+
+/* Same as setup_glsl_draw, but color management settings are guessing from a given context */
+int IMB_colormanagement_setup_glsl_draw_ctx(const bContext *C, int predivide)
+{
+	return IMB_colormanagement_setup_glsl_draw_from_space_ctx(C, NULL, predivide);
 }
 
 /* Finish GLSL-based display space conversion */
@@ -2827,7 +2852,7 @@ void IMB_colormanagement_finish_glsl_draw(void)
  * When there's no need to apply transform on 2D textures, use
  * IMB_colormanagement_finish_glsl_transform().
  */
-int IMB_colormanagement_setup_transform_from_role_glsl(int role)
+int IMB_colormanagement_setup_transform_from_role_glsl(int role, int predivide)
 {
 	OCIO_ConstProcessorRcPtr *processor;
 	ColorSpace *colorspace;
@@ -2836,7 +2861,7 @@ int IMB_colormanagement_setup_transform_from_role_glsl(int role)
 
 	processor = colorspace_to_scene_linear_processor(colorspace);
 
-	return OCIO_setupGLSLDraw(&global_glsl_state.transform_ocio_glsl_state, processor);
+	return OCIO_setupGLSLDraw(&global_glsl_state.transform_ocio_glsl_state, processor, predivide);
 }
 
 /* Finish GLSL-based color space conversion */
diff --git a/source/blender/windowmanager/intern/wm_dragdrop.c b/source/blender/windowmanager/intern/wm_dragdrop.c
index ed066117b28..0c78338c18a 100644
--- a/source/blender/windowmanager/intern/wm_dragdrop.c
+++ b/source/blender/windowmanager/intern/wm_dragdrop.c
@@ -323,7 +323,7 @@ void wm_drags_draw(bContext *C, wmWindow *win, rcti *rect)
 				drag_rect_minmax(rect, x, y, x + drag->sx, y + drag->sy);
 			else {
 				glColor4f(1.0, 1.0, 1.0, 0.65); /* this blends texture */
-				glaDrawPixelsTexScaled(x, y, drag->imb->x, drag->imb->y, GL_UNSIGNED_BYTE, GL_NEAREST, drag->imb->rect, drag->scale, drag->scale);
+				glaDrawPixelsTexScaled(x, y, drag->imb->x, drag->imb->y, GL_RGBA, GL_UNSIGNED_BYTE, GL_NEAREST, drag->imb->rect, drag->scale, drag->scale);
 			}
 		}
 		else {