Fix/Workaround #34854: render buffer update writes to wrong layer

Was caused by recent change in image_buffer_rect_update which
was writing data to ibuf-rect_float. Apparently, this buffer
could point to different render layer than came from RenderResult.

Made quick fix for this, which ends up in skipping float buffer
update in image_buffer_rect_update and skipping GLSL when image
has both byte and float buffers.

This will bring speed down a bit, but slower blender is better
than broken blender.

Proper fix will arrive later this week.

1 files changed, 8 insertions, 1 deletions

diff --git a/source/blender/editors/screen/glutil.c b/source/blender/editors/screen/glutil.c
index fecb3c58a2d..74086c7cc8b 100644
--- a/source/blender/editors/screen/glutil.c
+++ b/source/blender/editors/screen/glutil.c
@@ -998,7 +998,14 @@ void glaDrawImBuf_glsl_ctx(const bContext *C, ImBuf *ibuf, float x, float y, int
 	bool need_fallback = true;
 
 	/* Bytes and dithering are not supported on GLSL yet */
-	if (ibuf->rect_float && ibuf->dither == 0.0f) {
+
+	/* 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.
+	 */
+	if (ibuf->rect == NULL && ibuf->rect_float && ibuf->dither == 0.0f) {
 		if (IMB_colormanagement_setup_glsl_draw_from_ctx(C)) {
 			glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
 			glColor4f(1.0, 1.0, 1.0, 1.0);