WM: new offscreen window draw method to replace all existing methods.

For Blender 2.8 we had to be compatible with very old OpenGL versions, and
triple buffer was designed to work without offscreen rendering, by copying
the the backbuffer to a texture right before swapping. This way we could
avoid redrawing unchanged regions by copying them from this texture on the
next redraws. Triple buffer used to suffer from poor performance and driver
bugs on specific cards, so alternative draw methods remained available.

Now that we require newer OpenGL, we can have just a single draw method
that draw each region into an offscreen buffer, and then draws those to
the screen. This has some advantages:

* Poor 3D view performance when using Region Overlap should be solved now,
  since we can also cache overlapping regions in offscreen buffers.
* Page flip, anaglyph and interlace stereo drawing can be a little faster
  by avoiding a copy to an intermediate texture.
* The new 3D view drawing already writes to an offscreen buffer, which we
  can draw from directly instead of duplicating it to another buffer.
* Eventually we will be able to remove depth and stencil buffers from the
  window and save memory, though at the moment there are still some tools
  using it so it's not possible yet.
* This also fixes a bug with Eevee sampling not progressing with stereo
  drawing in the 3D viewport.

Differential Revision: https://developer.blender.org/D3061

12 files changed, 55 insertions, 84 deletions

diff --git a/source/blender/editors/include/ED_screen.h b/source/blender/editors/include/ED_screen.h
index b4857051c89..b5f1d947076 100644
--- a/source/blender/editors/include/ED_screen.h
+++ b/source/blender/editors/include/ED_screen.h
@@ -88,7 +88,7 @@ void    ED_region_info_draw(struct ARegion *ar, const char *text, float fill_col
 void    ED_region_info_draw_multiline(ARegion *ar, const char *text_array[], float fill_color[4], const bool full_redraw);
 void    ED_region_image_metadata_draw(int x, int y, struct ImBuf *ibuf, const rctf *frame, float zoomx, float zoomy);
 void    ED_region_grid_draw(struct ARegion *ar, float zoomx, float zoomy);
-float	ED_region_blend_factor(struct ARegion *ar);
+float	ED_region_blend_alpha(struct ARegion *ar);
 void	ED_region_visible_rect(struct ARegion *ar, struct rcti *rect);
 
 int     ED_region_snap_size_test(const struct ARegion *ar);
diff --git a/source/blender/editors/interface/interface_draw.c b/source/blender/editors/interface/interface_draw.c
index f84347b97a4..97491d365b7 100644
--- a/source/blender/editors/interface/interface_draw.c
+++ b/source/blender/editors/interface/interface_draw.c
@@ -644,7 +644,7 @@ void ui_draw_but_IMAGE(ARegion *UNUSED(ar), uiBut *but, uiWidgetColors *UNUSED(w
 	/* prevent drawing outside widget area */
 	GLint scissor[4];
 	glGetIntegerv(GL_SCISSOR_BOX, scissor);
-	glScissor(ar->winrct.xmin + rect->xmin, ar->winrct.ymin + rect->ymin, w, h);
+	glScissor(rect->xmin, rect->ymin, w, h);
 #endif
 	
 	glEnable(GL_BLEND);
@@ -773,7 +773,7 @@ static void histogram_draw_one(
 
 #define HISTOGRAM_TOT_GRID_LINES 4
 
-void ui_draw_but_HISTOGRAM(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wcol), const rcti *recti)
+void ui_draw_but_HISTOGRAM(ARegion *UNUSED(ar), uiBut *but, uiWidgetColors *UNUSED(wcol), const rcti *recti)
 {
 	Histogram *hist = (Histogram *)but->poin;
 	int res = hist->x_resolution;
@@ -800,8 +800,8 @@ void ui_draw_but_HISTOGRAM(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wcol)
 	/* need scissor test, histogram can draw outside of boundary */
 	GLint scissor[4];
 	glGetIntegerv(GL_SCISSOR_BOX, scissor);
-	glScissor(ar->winrct.xmin + (rect.xmin - 1),
-	          ar->winrct.ymin + (rect.ymin - 1),
+	glScissor((rect.xmin - 1),
+	          (rect.ymin - 1),
 	          (rect.xmax + 1) - (rect.xmin - 1),
 	          (rect.ymax + 1) - (rect.ymin - 1));
 
@@ -873,7 +873,7 @@ static void waveform_draw_one(float *waveform, int nbr, const float col[3])
 	GWN_batch_discard(batch);
 }
 
-void ui_draw_but_WAVEFORM(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wcol), const rcti *recti)
+void ui_draw_but_WAVEFORM(ARegion *UNUSED(ar), uiBut *but, uiWidgetColors *UNUSED(wcol), const rcti *recti)
 {
 	Scopes *scopes = (Scopes *)but->poin;
 	GLint scissor[4];
@@ -923,8 +923,8 @@ void ui_draw_but_WAVEFORM(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wcol),
 
 	/* need scissor test, waveform can draw outside of boundary */
 	glGetIntegerv(GL_SCISSOR_BOX, scissor);
-	glScissor(ar->winrct.xmin + (rect.xmin - 1),
-	          ar->winrct.ymin + (rect.ymin - 1),
+	glScissor((rect.xmin - 1),
+	          (rect.ymin - 1),
 	          (rect.xmax + 1) - (rect.xmin - 1),
 	          (rect.ymax + 1) - (rect.ymin - 1));
 
@@ -1160,7 +1160,7 @@ static void vectorscope_draw_target(unsigned int pos, float centerx, float cente
 	immEnd();
 }
 
-void ui_draw_but_VECTORSCOPE(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wcol), const rcti *recti)
+void ui_draw_but_VECTORSCOPE(ARegion *UNUSED(ar), uiBut *but, uiWidgetColors *UNUSED(wcol), const rcti *recti)
 {
 	const float skin_rad = DEG2RADF(123.0f); /* angle in radians of the skin tone line */
 	Scopes *scopes = (Scopes *)but->poin;
@@ -1195,8 +1195,8 @@ void ui_draw_but_VECTORSCOPE(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wco
 	/* need scissor test, hvectorscope can draw outside of boundary */
 	GLint scissor[4];
 	glGetIntegerv(GL_SCISSOR_BOX, scissor);
-	glScissor(ar->winrct.xmin + (rect.xmin - 1),
-	          ar->winrct.ymin + (rect.ymin - 1),
+	glScissor((rect.xmin - 1),
+	          (rect.ymin - 1),
 	          (rect.xmax + 1) - (rect.xmin - 1),
 	          (rect.ymax + 1) - (rect.ymin - 1));
 	
@@ -1622,12 +1622,13 @@ void ui_draw_but_CURVE(ARegion *ar, uiBut *but, uiWidgetColors *wcol, const rcti
 	GLint scissor[4];
 	glGetIntegerv(GL_SCISSOR_BOX, scissor);
 	rcti scissor_new = {
-		.xmin = ar->winrct.xmin + rect->xmin,
-		.ymin = ar->winrct.ymin + rect->ymin,
-		.xmax = ar->winrct.xmin + rect->xmax,
-		.ymax = ar->winrct.ymin + rect->ymax
+		.xmin = rect->xmin,
+		.ymin = rect->ymin,
+		.xmax = rect->xmax,
+		.ymax = rect->ymax
 	};
-	BLI_rcti_isect(&scissor_new, &ar->winrct, &scissor_new);
+	rcti scissor_region = {0, ar->winx, 0, ar->winy};
+	BLI_rcti_isect(&scissor_new, &scissor_region, &scissor_new);
 	glScissor(scissor_new.xmin,
 	          scissor_new.ymin,
 	          BLI_rcti_size_x(&scissor_new),
@@ -1822,7 +1823,7 @@ void ui_draw_but_CURVE(ARegion *ar, uiBut *but, uiWidgetColors *wcol, const rcti
 	immUnbindProgram();
 }
 
-void ui_draw_but_TRACKPREVIEW(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wcol), const rcti *recti)
+void ui_draw_but_TRACKPREVIEW(ARegion *UNUSED(ar), uiBut *but, uiWidgetColors *UNUSED(wcol), const rcti *recti)
 {
 	bool ok = false;
 	MovieClipScopes *scopes = (MovieClipScopes *)but->poin;
@@ -1843,8 +1844,8 @@ void ui_draw_but_TRACKPREVIEW(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wc
 	/* need scissor test, preview image can draw outside of boundary */
 	GLint scissor[4];
 	glGetIntegerv(GL_SCISSOR_BOX, scissor);
-	glScissor(ar->winrct.xmin + (rect.xmin - 1),
-	          ar->winrct.ymin + (rect.ymin - 1),
+	glScissor((rect.xmin - 1),
+	          (rect.ymin - 1),
 	          (rect.xmax + 1) - (rect.xmin - 1),
 	          (rect.ymax + 1) - (rect.ymin - 1));
 
@@ -1881,7 +1882,7 @@ void ui_draw_but_TRACKPREVIEW(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wc
 		gpuPushMatrix();
 
 		/* draw content of pattern area */
-		glScissor(ar->winrct.xmin + rect.xmin, ar->winrct.ymin + rect.ymin, scissor[2], scissor[3]);
+		glScissor(rect.xmin, rect.ymin, scissor[2], scissor[3]);
 
 		if (width > 0 && height > 0) {
 			ImBuf *drawibuf = scopes->track_preview;
@@ -1898,8 +1899,8 @@ void ui_draw_but_TRACKPREVIEW(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wc
 
 			/* draw cross for pixel position */
 			gpuTranslate2f(rect.xmin + scopes->track_pos[0], rect.ymin + scopes->track_pos[1]);
-			glScissor(ar->winrct.xmin + rect.xmin,
-			          ar->winrct.ymin + rect.ymin,
+			glScissor(rect.xmin,
+			          rect.ymin,
 			          BLI_rctf_size_x(&rect),
 			          BLI_rctf_size_y(&rect));
 
@@ -1977,13 +1978,15 @@ void ui_draw_but_NODESOCKET(ARegion *ar, uiBut *but, uiWidgetColors *UNUSED(wcol
 	glGetIntegerv(GL_SCISSOR_BOX, scissor);
 	
 	rcti scissor_new = {
-		.xmin = ar->winrct.xmin + recti->xmin,
-		.ymin = ar->winrct.ymin + recti->ymin,
-		.xmax = ar->winrct.xmin + recti->xmax,
-		.ymax = ar->winrct.ymin + recti->ymax
+		.xmin = recti->xmin,
+		.ymin = recti->ymin,
+		.xmax = recti->xmax,
+		.ymax = recti->ymax
 	};
 
-	BLI_rcti_isect(&scissor_new, &ar->winrct, &scissor_new);
+	rcti scissor_region = {0, ar->winx, 0, ar->winy};
+
+	BLI_rcti_isect(&scissor_new, &scissor_region, &scissor_new);
 	glScissor(scissor_new.xmin,
 	          scissor_new.ymin,
 	          BLI_rcti_size_x(&scissor_new),
diff --git a/source/blender/editors/interface/interface_region_popup.c b/source/blender/editors/interface/interface_region_popup.c
index b13d9b0448c..56611627a67 100644
--- a/source/blender/editors/interface/interface_region_popup.c
+++ b/source/blender/editors/interface/interface_region_popup.c
@@ -300,7 +300,7 @@ static void ui_block_position(wmWindow *window, ARegion *butregion, uiBut *but,
 /** \name Menu Block Creation
  * \{ */
 
-static void ui_block_region_draw(const bContext *C, ARegion *ar)
+static void ui_block_region_refresh(const bContext *C, ARegion *ar)
 {
 	ScrArea *ctx_area = CTX_wm_area(C);
 	ARegion *ctx_region = CTX_wm_region(C);
@@ -331,6 +331,11 @@ static void ui_block_region_draw(const bContext *C, ARegion *ar)
 
 	CTX_wm_area_set((bContext *)C, ctx_area);
 	CTX_wm_region_set((bContext *)C, ctx_region);
+}
+
+static void ui_block_region_draw(const bContext *C, ARegion *ar)
+{
+	uiBlock *block;
 
 	for (block = ar->uiblocks.first; block; block = block->next)
 		UI_block_draw(C, block);
@@ -660,6 +665,7 @@ uiPopupBlockHandle *ui_popup_block_create(
 
 	memset(&type, 0, sizeof(ARegionType));
 	type.draw = ui_block_region_draw;
+	type.refresh = ui_block_region_refresh;
 	type.regionid = RGN_TYPE_TEMPORARY;
 	ar->type = &type;
 
diff --git a/source/blender/editors/interface/resources.c b/source/blender/editors/interface/resources.c
index ade69050622..d284bde6ce6 100644
--- a/source/blender/editors/interface/resources.c
+++ b/source/blender/editors/interface/resources.c
@@ -2171,10 +2171,6 @@ void init_userdef_do_versions(void)
 				strcpy(km->idname, "Property Editor");
 		}
 	}
-	if (!USER_VERSION_ATLEAST(250, 16)) {
-		if (U.wmdrawmethod == USER_DRAW_TRIPLE)
-			U.wmdrawmethod = USER_DRAW_AUTOMATIC;
-	}
 	
 	if (!USER_VERSION_ATLEAST(252, 3)) {
 		if (U.flag & USER_LMOUSESELECT) 
diff --git a/source/blender/editors/screen/area.c b/source/blender/editors/screen/area.c
index 0f9378d0a41..a17f7ec6255 100644
--- a/source/blender/editors/screen/area.c
+++ b/source/blender/editors/screen/area.c
@@ -1075,18 +1075,16 @@ static void region_overlap_fix(ScrArea *sa, ARegion *ar)
 }
 
 /* overlapping regions only in the following restricted cases */
-static bool region_is_overlap(wmWindow *win, ScrArea *sa, ARegion *ar)
+static bool region_is_overlap(ScrArea *sa, ARegion *ar)
 {
 	if (U.uiflag2 & USER_REGION_OVERLAP) {
-		if (WM_is_draw_triple(win)) {
-			if (ELEM(sa->spacetype, SPACE_VIEW3D, SPACE_SEQ)) {
-				if (ELEM(ar->regiontype, RGN_TYPE_TOOLS, RGN_TYPE_UI, RGN_TYPE_TOOL_PROPS))
-					return 1;
-			}
-			else if (sa->spacetype == SPACE_IMAGE) {
-				if (ELEM(ar->regiontype, RGN_TYPE_TOOLS, RGN_TYPE_UI, RGN_TYPE_TOOL_PROPS, RGN_TYPE_PREVIEW))
-					return 1;
-			}
+		if (ELEM(sa->spacetype, SPACE_VIEW3D, SPACE_SEQ)) {
+			if (ELEM(ar->regiontype, RGN_TYPE_TOOLS, RGN_TYPE_UI, RGN_TYPE_TOOL_PROPS))
+				return 1;
+		}
+		else if (sa->spacetype == SPACE_IMAGE) {
+			if (ELEM(ar->regiontype, RGN_TYPE_TOOLS, RGN_TYPE_UI, RGN_TYPE_TOOL_PROPS, RGN_TYPE_PREVIEW))
+				return 1;
 		}
 	}
 
@@ -1113,7 +1111,7 @@ static void region_rect_recursive(wmWindow *win, ScrArea *sa, ARegion *ar, rcti
 	alignment = ar->alignment & ~RGN_SPLIT_PREV;
 	
 	/* set here, assuming userpref switching forces to call this again */
-	ar->overlap = region_is_overlap(win, sa, ar);
+	ar->overlap = region_is_overlap(sa, ar);
 
 	/* clear state flags first */
 	ar->flag &= ~RGN_FLAG_TOO_SMALL;
@@ -2062,14 +2060,11 @@ void ED_region_panels(const bContext *C, ARegion *ar, const char *context, int c
 	if (ar->overlap) {
 		/* view should be in pixelspace */
 		UI_view2d_view_restore(C);
-		glEnable(GL_BLEND);
-		Gwn_VertFormat *format = immVertexFormat();
-		unsigned int pos = GWN_vertformat_attr_add(format, "pos", GWN_COMP_I32, 2, GWN_FETCH_INT_TO_FLOAT);
-		immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
-		immUniformThemeColor((ar->type->regionid == RGN_TYPE_PREVIEW) ? TH_PREVIEW_BACK : TH_BACK);
-		immRecti(pos, 0, 0, BLI_rcti_size_x(&ar->winrct), BLI_rcti_size_y(&ar->winrct) + 1);
-		immUnbindProgram();
-		glDisable(GL_BLEND);
+
+		float back[4];
+		UI_GetThemeColor4fv((ar->type->regionid == RGN_TYPE_PREVIEW) ? TH_PREVIEW_BACK : TH_BACK, back);
+		glClearColor(back[3] * back[0], back[3] * back[1], back[3] * back[2], back[3]);
+		glClear(GL_COLOR_BUFFER_BIT);
 	}
 	else {
 		UI_ThemeClearColor((ar->type->regionid == RGN_TYPE_PREVIEW) ? TH_PREVIEW_BACK : TH_BACK);
@@ -2278,7 +2273,7 @@ void ED_region_info_draw_multiline(ARegion *ar, const char *text_array[], float
 
 	/* setup scissor */
 	glGetIntegerv(GL_SCISSOR_BOX, scissor);
-	glScissor(ar->winrct.xmin + rect.xmin, ar->winrct.ymin + rect.ymin,
+	glScissor(rect.xmin, rect.ymin,
 	          BLI_rcti_size_x(&rect) + 1, BLI_rcti_size_y(&rect) + 1);
 
 	glEnable(GL_BLEND);
diff --git a/source/blender/editors/screen/screen_draw.c b/source/blender/editors/screen/screen_draw.c
index 4b388059ca3..fec39ade110 100644
--- a/source/blender/editors/screen/screen_draw.c
+++ b/source/blender/editors/screen/screen_draw.c
@@ -438,8 +438,6 @@ void ED_screen_draw_edges(wmWindow *win)
 
 	ScrArea *sa;
 
-	wmWindowViewport(win);
-
 	unsigned int pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
 	immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
 
diff --git a/source/blender/editors/screen/screen_edit.c b/source/blender/editors/screen/screen_edit.c
index ab58d4c8ebf..c7d1605cbbf 100644
--- a/source/blender/editors/screen/screen_edit.c
+++ b/source/blender/editors/screen/screen_edit.c
@@ -908,7 +908,7 @@ void ED_region_exit(bContext *C, ARegion *ar)
 
 	WM_event_remove_handlers(C, &ar->handlers);
 	WM_event_modal_handler_region_replace(win, ar, NULL);
-	ar->visible = 0;
+	WM_draw_region_free(ar);
 	
 	if (ar->headerstr) {
 		MEM_freeN(ar->headerstr);
diff --git a/source/blender/editors/screen/screen_ops.c b/source/blender/editors/screen/screen_ops.c
index 7dab2c7c3db..847afb5f9f1 100644
--- a/source/blender/editors/screen/screen_ops.c
+++ b/source/blender/editors/screen/screen_ops.c
@@ -4207,7 +4207,7 @@ typedef struct RegionAlphaInfo {
 #define TIMEOUT		0.2f
 #define TIMESTEP	0.04f
 
-float ED_region_blend_factor(ARegion *ar)
+float ED_region_blend_alpha(ARegion *ar)
 {
 	/* check parent too */
 	if (ar->regiontimer == NULL && (ar->alignment & RGN_SPLIT_PREV) && ar->prev) {
diff --git a/source/blender/editors/space_outliner/outliner_draw.c b/source/blender/editors/space_outliner/outliner_draw.c
index fad35060d72..6875971de24 100644
--- a/source/blender/editors/space_outliner/outliner_draw.c
+++ b/source/blender/editors/space_outliner/outliner_draw.c
@@ -1788,7 +1788,7 @@ static void outliner_draw_tree(
 		CLAMP_MIN(mask_x, 0);
 
 		glGetFloatv(GL_SCISSOR_BOX, scissor);
-		glScissor(ar->winrct.xmin, ar->winrct.ymin, mask_x, ar->winy);
+		glScissor(0, 0, mask_x, ar->winy);
 	}
 
 	// gray hierarchy lines
diff --git a/source/blender/editors/space_view3d/space_view3d.c b/source/blender/editors/space_view3d/space_view3d.c
index 4fb4193517b..1a23dd0feff 100644
--- a/source/blender/editors/space_view3d/space_view3d.c
+++ b/source/blender/editors/space_view3d/space_view3d.c
@@ -545,13 +545,6 @@ static void view3d_main_region_exit(wmWindowManager *wm, ARegion *ar)
 		GPU_offscreen_free(rv3d->gpuoffscreen);
 		rv3d->gpuoffscreen = NULL;
 	}
-	
-	if (rv3d->viewport) {
-		DRW_opengl_context_enable();
-		GPU_viewport_free(rv3d->viewport);
-		DRW_opengl_context_disable();
-		rv3d->viewport = NULL;
-	}
 }
 
 static int view3d_ob_drop_poll(bContext *UNUSED(C), wmDrag *drag, const wmEvent *UNUSED(event))
@@ -729,11 +722,6 @@ static void view3d_main_region_free(ARegion *ar)
 		if (rv3d->gpuoffscreen) {
 			GPU_offscreen_free(rv3d->gpuoffscreen);
 		}
-		if (rv3d->viewport) {
-			DRW_opengl_context_enable();
-			GPU_viewport_free(rv3d->viewport);
-			DRW_opengl_context_disable();
-		}
 
 		MEM_freeN(rv3d);
 		ar->regiondata = NULL;
@@ -758,7 +746,6 @@ static void *view3d_main_region_duplicate(void *poin)
 		new->sms = NULL;
 		new->smooth_timer = NULL;
 		new->compositor = NULL;
-		new->viewport = NULL;
 		
 		return new;
 	}
diff --git a/source/blender/editors/space_view3d/view3d_draw.c b/source/blender/editors/space_view3d/view3d_draw.c
index 166684e7230..3bc86a82afd 100644
--- a/source/blender/editors/space_view3d/view3d_draw.c
+++ b/source/blender/editors/space_view3d/view3d_draw.c
@@ -1259,19 +1259,8 @@ RenderEngineType *ED_view3d_engine_type(Scene *scene, int drawtype)
 void view3d_main_region_draw(const bContext *C, ARegion *ar)
 {
 	View3D *v3d = CTX_wm_view3d(C);
-	RegionView3D *rv3d = ar->regiondata;
-
-	if (!rv3d->viewport) {
-		rv3d->viewport = GPU_viewport_create();
-	}
 
-	GPU_viewport_bind(rv3d->viewport, &ar->winrct);
 	view3d_draw_view(C, ar);
-	GPU_viewport_unbind(rv3d->viewport);
-
-	rcti rect = ar->winrct;
-	BLI_rcti_translate(&rect, -ar->winrct.xmin, -ar->winrct.ymin);
-	GPU_viewport_draw_to_screen(rv3d->viewport, &rect);
 
 	GPU_free_images_old();
 	GPU_pass_cache_garbage_collect();
@@ -1279,7 +1268,6 @@ void view3d_main_region_draw(const bContext *C, ARegion *ar)
 	v3d->flag |= V3D_INVALID_BACKBUF;
 }
 
-
 /* -------------------------------------------------------------------- */
 
 /** \name Offscreen Drawing
diff --git a/source/blender/editors/space_view3d/view3d_draw_legacy.c b/source/blender/editors/space_view3d/view3d_draw_legacy.c
index eecd185aedf..15359dcd6d6 100644
--- a/source/blender/editors/space_view3d/view3d_draw_legacy.c
+++ b/source/blender/editors/space_view3d/view3d_draw_legacy.c
@@ -266,8 +266,6 @@ static void backdrawview3d(
 
 	if (rv3d->gpuoffscreen)
 		GPU_offscreen_unbind(rv3d->gpuoffscreen, true);
-	else
-		ar->swap = 0; /* mark invalid backbuf for wm draw */
 
 	v3d->flag &= ~V3D_INVALID_BACKBUF;