OpenGL: clean up glActiveTexture usage

Removed some of my earlier glActiveTexture calls. After reviewing the
code I now trust that GL_TEXTURE0 is active by default. Fewer GL calls,
same results.

Fixed some misuse of glActiveTexture & glUniformi, mostly my fault.
Caught by --debug-gpu on Windows. Don't know why this appeared to be
working previously!

Plus some easy cleanup nearby.

5 files changed, 38 insertions, 48 deletions

diff --git a/source/blender/editors/space_view3d/drawobject.c b/source/blender/editors/space_view3d/drawobject.c
index 7426b20fe03..5d7282ce369 100644
--- a/source/blender/editors/space_view3d/drawobject.c
+++ b/source/blender/editors/space_view3d/drawobject.c
@@ -652,12 +652,10 @@ static void draw_empty_image(Object *ob, const short dflag, const unsigned char
 	const float ob_alpha = ob->col[3];
 	float width, height;
 
-	const int texUnit = GL_TEXTURE0;
 	int bindcode = 0;
 
 	if (ima) {
 		if (ob_alpha > 0.0f) {
-			glActiveTexture(texUnit);
 			bindcode = GPU_verify_image(ima, ob->iuser, GL_TEXTURE_2D, 0, false, false, false);
 			/* don't bother drawing the image if alpha = 0 */
 		}
@@ -694,7 +692,7 @@ static void draw_empty_image(Object *ob, const short dflag, const unsigned char
 		unsigned texCoord = add_attrib(format, "texCoord", GL_FLOAT, 2, KEEP_FLOAT);
 		immBindBuiltinProgram(GPU_SHADER_3D_IMAGE_MODULATE_ALPHA);
 		immUniform1f("alpha", ob_alpha);
-		immUniform1i("image", texUnit);
+		immUniform1i("image", 0); /* default GL_TEXTURE0 unit */
 
 		immBegin(GL_TRIANGLE_FAN, 4);
 		immAttrib2f(texCoord, 0.0f, 0.0f);
diff --git a/source/blender/gpu/intern/gpu_shader.c b/source/blender/gpu/intern/gpu_shader.c
index 9d1c3b007c9..21fd5385f79 100644
--- a/source/blender/gpu/intern/gpu_shader.c
+++ b/source/blender/gpu/intern/gpu_shader.c
@@ -578,7 +578,6 @@ void GPU_shader_geometry_stage_primitive_io(GPUShader *shader, int input, int ou
 
 void GPU_shader_uniform_texture(GPUShader *UNUSED(shader), int location, GPUTexture *tex)
 {
-	GLenum arbnumber;
 	int number = GPU_texture_bound_number(tex);
 	int bindcode = GPU_texture_opengl_bindcode(tex);
 	int target = GPU_texture_target(tex);
@@ -594,16 +593,18 @@ void GPU_shader_uniform_texture(GPUShader *UNUSED(shader), int location, GPUText
 	if (location == -1)
 		return;
 
-	arbnumber = (GLenum)((GLuint)GL_TEXTURE0 + number);
+	if (number != 0)
+		glActiveTexture(GL_TEXTURE0 + number);
 
-	if (number != 0) glActiveTexture(arbnumber);
 	if (bindcode != 0)
 		glBindTexture(target, bindcode);
 	else
 		GPU_invalid_tex_bind(target);
+
 	glUniform1i(location, number);
-	glEnable(target);
-	if (number != 0) glActiveTexture(GL_TEXTURE0);
+
+	if (number != 0)
+		glActiveTexture(GL_TEXTURE0);
 }
 
 int GPU_shader_get_attribute(GPUShader *shader, const char *name)
diff --git a/source/blender/gpu/intern/gpu_texture.c b/source/blender/gpu/intern/gpu_texture.c
index c6cf4dec22e..6956a815ac5 100644
--- a/source/blender/gpu/intern/gpu_texture.c
+++ b/source/blender/gpu/intern/gpu_texture.c
@@ -616,15 +616,18 @@ void GPU_texture_bind(GPUTexture *tex, int number)
 	if (number < 0)
 		return;
 
-	GLenum arbnumber = (GLenum)((GLuint)GL_TEXTURE0 + number);
-	if (number != 0) glActiveTexture(arbnumber);
-	if (tex->bindcode != 0) {
+	if (number != 0)
+		glActiveTexture(GL_TEXTURE0 + number);
+
+	if (tex->bindcode != 0)
 		glBindTexture(tex->target_base, tex->bindcode);
-	}
 	else
 		GPU_invalid_tex_bind(tex->target_base);
-	glEnable(tex->target_base);
-	if (number != 0) glActiveTexture(GL_TEXTURE0);
+
+	glEnable(tex->target_base); /* TODO: remove this line once we're using GLSL everywhere */
+
+	if (number != 0)
+		glActiveTexture(GL_TEXTURE0);
 
 	tex->number = number;
 }
@@ -639,11 +642,14 @@ void GPU_texture_unbind(GPUTexture *tex)
 	if (tex->number == -1)
 		return;
 
-	GLenum arbnumber = (GLenum)((GLuint)GL_TEXTURE0 + tex->number);
-	if (tex->number != 0) glActiveTexture(arbnumber);
+	if (tex->number != 0)
+		glActiveTexture(GL_TEXTURE0 + tex->number);
+
 	glBindTexture(tex->target_base, 0);
-	glDisable(tex->target_base);
-	if (tex->number != 0) glActiveTexture(GL_TEXTURE0);
+	glDisable(tex->target_base); /* TODO: remove this line */
+
+	if (tex->number != 0)
+		glActiveTexture(GL_TEXTURE0);
 
 	tex->number = -1;
 }
@@ -663,25 +669,19 @@ void GPU_texture_filter_mode(GPUTexture *tex, bool compare, bool use_filter)
 	if (tex->number == -1)
 		return;
 
-	GLenum arbnumber = (GLenum)((GLuint)GL_TEXTURE0 + tex->number);
-	if (tex->number != 0) glActiveTexture(arbnumber);
+	if (tex->number != 0)
+		glActiveTexture(GL_TEXTURE0 + tex->number);
 
 	if (tex->depth) {
-		if (compare)
-			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_COMPARE_R_TO_TEXTURE);
-		else
-			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, GL_NONE);
+		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_COMPARE_MODE, compare ? GL_COMPARE_R_TO_TEXTURE : GL_NONE);
 	}
 
-	if (use_filter) {
-		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
-		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-	}
-	else {
-		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
-		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
-	}
-	if (tex->number != 0) glActiveTexture(GL_TEXTURE0);
+	GLenum filter = use_filter ? GL_LINEAR : GL_NEAREST;
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, filter);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, filter);
+
+	if (tex->number != 0)
+		glActiveTexture(GL_TEXTURE0);
 }
 
 void GPU_texture_free(GPUTexture *tex)
diff --git a/source/blender/gpu/intern/gpu_viewport.c b/source/blender/gpu/intern/gpu_viewport.c
index 6cad0506cf4..ea54f3cc57c 100644
--- a/source/blender/gpu/intern/gpu_viewport.c
+++ b/source/blender/gpu/intern/gpu_viewport.c
@@ -89,9 +89,6 @@ void GPU_viewport_debug_depth_draw(GPUViewport *viewport, const float znear, con
 	const float w = (float)GPU_texture_width(viewport->debug_depth);
 	const float h = (float)GPU_texture_height(viewport->debug_depth);
 
-	const int activeTex = GL_TEXTURE0;
-	glActiveTexture(activeTex);
-
 	VertexFormat *format = immVertexFormat();
 	unsigned texcoord = add_attrib(format, "texCoord", GL_FLOAT, 2, KEEP_FLOAT);
 	unsigned pos = add_attrib(format, "pos", GL_FLOAT, 2, KEEP_FLOAT);
@@ -102,7 +99,7 @@ void GPU_viewport_debug_depth_draw(GPUViewport *viewport, const float znear, con
 
 	immUniform1f("znear", znear);
 	immUniform1f("zfar", zfar);
-	immUniform1i("image", activeTex);
+	immUniform1i("image", 0); /* default GL_TEXTURE0 unit */
 
 	immBegin(GL_QUADS, 4);
 
diff --git a/source/blender/windowmanager/intern/wm_stereo.c b/source/blender/windowmanager/intern/wm_stereo.c
index 3dd6c34bc98..f625423caa8 100644
--- a/source/blender/windowmanager/intern/wm_stereo.c
+++ b/source/blender/windowmanager/intern/wm_stereo.c
@@ -173,9 +173,6 @@ static void wm_method_draw_stereo3d_sidebyside(wmWindow *win)
 	int soffx;
 	bool cross_eyed = (win->stereo3d_format->flag & S3D_SIDEBYSIDE_CROSSEYED) != 0;
 
-	const int activeTex = GL_TEXTURE0;
-	glActiveTexture(activeTex);
-
 	VertexFormat *format = immVertexFormat();
 	unsigned texcoord = add_attrib(format, "texCoord", GL_FLOAT, 2, KEEP_FLOAT);
 	unsigned pos = add_attrib(format, "pos", GL_FLOAT, 2, KEEP_FLOAT);
@@ -217,7 +214,7 @@ static void wm_method_draw_stereo3d_sidebyside(wmWindow *win)
 		glBindTexture(triple->target, triple->bind);
 
 		immUniform1f("alpha", 1.0f);
-		immUniform1i("image", activeTex);
+		immUniform1i("image", 0); /* default GL_TEXTURE0 unit */
 
 		immBegin(GL_QUADS, 4);
 
@@ -249,9 +246,6 @@ static void wm_method_draw_stereo3d_topbottom(wmWindow *win)
 	int view;
 	int soffy;
 
-	const int activeTex = GL_TEXTURE0;
-	glActiveTexture(activeTex);
-
 	VertexFormat *format = immVertexFormat();
 	unsigned texcoord = add_attrib(format, "texCoord", GL_FLOAT, 2, KEEP_FLOAT);
 	unsigned pos = add_attrib(format, "pos", GL_FLOAT, 2, KEEP_FLOAT);
@@ -290,7 +284,7 @@ static void wm_method_draw_stereo3d_topbottom(wmWindow *win)
 		glBindTexture(triple->target, triple->bind);
 
 		immUniform1f("alpha", 1.0f);
-		immUniform1i("image", activeTex);
+		immUniform1i("image", 0); /* default GL_TEXTURE0 unit */
 
 		immBegin(GL_QUADS, 4);
 
@@ -339,9 +333,9 @@ void wm_method_draw_stereo3d(const bContext *UNUSED(C), wmWindow *win)
 
 static bool wm_stereo3d_quadbuffer_supported(void)
 {
-	int gl_stereo = 0;
-	glGetBooleanv(GL_STEREO, (GLboolean *)&gl_stereo);
-	return gl_stereo != 0;
+	GLboolean stereo = GL_FALSE;
+	glGetBooleanv(GL_STEREO, &stereo);
+	return stereo == GL_TRUE;
 }
 
 static bool wm_stereo3d_is_fullscreen_required(eStereoDisplayMode stereo_display)