Draw Manager: fix glitches when setting 3d cursor position by click.

source/blender/draw/intern/draw_view.c

@@ -553,7 +553,7 @@ void DRW_draw_background(void)
 		/* Gradient background Color */
 		gpuMatrixBegin3D(); /* TODO: finish 2D API */
 
-		glClear(GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
+		glDisable(GL_DEPTH_TEST);
 
 		VertexFormat *format = immVertexFormat();
 		unsigned pos = add_attrib(format, "pos", COMP_F32, 2, KEEP_FLOAT);
@@ -578,6 +578,8 @@ void DRW_draw_background(void)
 		immUnbindProgram();
 
 		gpuMatrixEnd();
+
+		glClear(GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
 	}
 	else {
 		/* Solid background Color */

source/blender/gpu/intern/gpu_viewport.c

@@ -289,6 +289,7 @@ void GPU_viewport_unbind(GPUViewport *viewport)
 		GPU_framebuffer_restore();
 
 		glEnable(GL_SCISSOR_TEST);
+		glDisable(GL_DEPTH_TEST);
 
 		/* This might be bandwidth limiting */
 		draw_ofs_to_screen(viewport);