Fix T49861: Interlace stereo is broken in 2.78

This is a regression introduced in rB5bd9e832

It looks more like a hack than a proper fix, but the shader logic
changed a lot for blender2.8, so I would rather do the elegant fix
there, while leaving master working.

If we ever do a 2.78b (or 2.79) this should get in.

3 files changed, 21 insertions, 10 deletions

diff --git a/source/blender/windowmanager/intern/wm_draw.c b/source/blender/windowmanager/intern/wm_draw.c
index 3825db14e93..77ffa46b990 100644
--- a/source/blender/windowmanager/intern/wm_draw.c
+++ b/source/blender/windowmanager/intern/wm_draw.c
@@ -430,7 +430,7 @@ static int wm_triple_gen_textures(wmWindow *win, wmDrawTriple *triple)
 	return 1;
 }
 
-void wm_triple_draw_textures(wmWindow *win, wmDrawTriple *triple, float alpha)
+void wm_triple_draw_textures(wmWindow *win, wmDrawTriple *triple, float alpha, bool is_interlace)
 {
 	const int sizex = WM_window_pixels_x(win);
 	const int sizey = WM_window_pixels_y(win);
@@ -451,7 +451,13 @@ void wm_triple_draw_textures(wmWindow *win, wmDrawTriple *triple, float alpha)
 		halfy /= triple->y;
 	}
 
-	GPU_basic_shader_bind((triple->target == GL_TEXTURE_2D) ? GPU_SHADER_TEXTURE_2D : GPU_SHADER_TEXTURE_RECT);
+	/* interlace stereo buffer bind the shader before calling wm_triple_draw_textures */
+	if (is_interlace) {
+		glEnable(triple->target);
+	}
+	else {
+		GPU_basic_shader_bind((triple->target == GL_TEXTURE_2D) ? GPU_SHADER_TEXTURE_2D : GPU_SHADER_TEXTURE_RECT);
+	}
 
 	glBindTexture(triple->target, triple->bind);
 
@@ -472,7 +478,12 @@ void wm_triple_draw_textures(wmWindow *win, wmDrawTriple *triple, float alpha)
 
 	glBindTexture(triple->target, 0);
 
-	GPU_basic_shader_bind(GPU_SHADER_USE_COLOR);
+	if (is_interlace) {
+		glDisable(triple->target);
+	}
+	else {
+		GPU_basic_shader_bind(GPU_SHADER_USE_COLOR);
+	}
 }
 
 static void wm_triple_copy_textures(wmWindow *win, wmDrawTriple *triple)
@@ -495,7 +506,7 @@ static void wm_draw_region_blend(wmWindow *win, ARegion *ar, wmDrawTriple *tripl
 		wmSubWindowScissorSet(win, win->screen->mainwin, &ar->winrct, true);
 
 		glEnable(GL_BLEND);
-		wm_triple_draw_textures(win, triple, 1.0f - fac);
+		wm_triple_draw_textures(win, triple, 1.0f - fac, false);
 		glDisable(GL_BLEND);
 	}
 }
@@ -516,7 +527,7 @@ static void wm_method_draw_triple(bContext *C, wmWindow *win)
 
 		wmSubWindowSet(win, screen->mainwin);
 
-		wm_triple_draw_textures(win, drawdata->triple, 1.0f);
+		wm_triple_draw_textures(win, drawdata->triple, 1.0f, false);
 	}
 	else {
 		/* we run it when we start OR when we turn stereo on */
@@ -656,7 +667,7 @@ static void wm_method_draw_triple_multiview(bContext *C, wmWindow *win, StereoVi
 
 				wmSubWindowSet(win, screen->mainwin);
 
-				wm_triple_draw_textures(win, drawdata->triple, 1.0f);
+				wm_triple_draw_textures(win, drawdata->triple, 1.0f, false);
 			}
 		}
 		else {
diff --git a/source/blender/windowmanager/intern/wm_stereo.c b/source/blender/windowmanager/intern/wm_stereo.c
index 1c1c2ad35af..46cee907991 100644
--- a/source/blender/windowmanager/intern/wm_stereo.c
+++ b/source/blender/windowmanager/intern/wm_stereo.c
@@ -77,7 +77,7 @@ static void wm_method_draw_stereo3d_pageflip(wmWindow *win)
 		else //STEREO_RIGHT_ID
 			glDrawBuffer(GL_BACK_RIGHT);
 
-		wm_triple_draw_textures(win, drawdata->triple, 1.0f);
+		wm_triple_draw_textures(win, drawdata->triple, 1.0f, false);
 	}
 
 	glDrawBuffer(GL_BACK);
@@ -120,7 +120,7 @@ static void wm_method_draw_stereo3d_interlace(wmWindow *win)
 				break;
 		}
 
-		wm_triple_draw_textures(win, drawdata->triple, 1.0f);
+		wm_triple_draw_textures(win, drawdata->triple, 1.0f, true);
 		GPU_basic_shader_bind(GPU_SHADER_USE_COLOR);
 	}
 	interlace_prev_type = interlace_type;
@@ -157,7 +157,7 @@ static void wm_method_draw_stereo3d_anaglyph(wmWindow *win)
 				break;
 		}
 
-		wm_triple_draw_textures(win, drawdata->triple, 1.0f);
+		wm_triple_draw_textures(win, drawdata->triple, 1.0f, false);
 
 		glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
 	}
diff --git a/source/blender/windowmanager/wm_draw.h b/source/blender/windowmanager/wm_draw.h
index 0f125309045..5257bba45ff 100644
--- a/source/blender/windowmanager/wm_draw.h
+++ b/source/blender/windowmanager/wm_draw.h
@@ -56,7 +56,7 @@ void		wm_draw_region_clear	(struct wmWindow *win, struct ARegion *ar);
 
 void		wm_tag_redraw_overlay	(struct wmWindow *win, struct ARegion *ar);
 
-void		wm_triple_draw_textures	(struct wmWindow *win, struct wmDrawTriple *triple, float alpha);
+void		wm_triple_draw_textures	(struct wmWindow *win, struct wmDrawTriple *triple, float alpha, bool is_interlace);
 
 void		wm_draw_data_free		(struct wmWindow *win);