Fix T95725: Changing render slot doesn't update displayed image.

Fixed by checking the requested pass, layer and view against the
previous used one.

2 files changed, 26 insertions, 0 deletions

diff --git a/source/blender/draw/engines/image/image_drawing_mode.hh b/source/blender/draw/engines/image/image_drawing_mode.hh
index 0aaf0ca9f24..0c638ef15c2 100644
--- a/source/blender/draw/engines/image/image_drawing_mode.hh
+++ b/source/blender/draw/engines/image/image_drawing_mode.hh
@@ -474,6 +474,9 @@ template<typename TextureMethod> class ScreenSpaceDrawingMode : public AbstractD
     method.update_screen_space_bounds(region);
     method.update_screen_uv_bounds();
 
+    // Check for changes in the image user compared to the last time.
+    instance_data->update_image_user(iuser);
+
     // Step: Update the GPU textures based on the changes in the image.
     instance_data->update_gpu_texture_allocations();
     update_textures(*instance_data, image, iuser);
diff --git a/source/blender/draw/engines/image/image_instance_data.hh b/source/blender/draw/engines/image/image_instance_data.hh
index 77b771a9110..a2367c687b5 100644
--- a/source/blender/draw/engines/image/image_instance_data.hh
+++ b/source/blender/draw/engines/image/image_instance_data.hh
@@ -40,6 +40,8 @@ constexpr int SCREEN_SPACE_DRAWING_MODE_TEXTURE_LEN = 1;
 
 struct IMAGE_InstanceData {
   struct Image *image;
+  /** Copy of the last image user to detect iuser differences that require a full update. */
+  struct ImageUser last_image_user;
 
   PartialImageUpdater partial_update;
 
@@ -108,6 +110,27 @@ struct IMAGE_InstanceData {
     }
   }
 
+  void update_image_user(const ImageUser *image_user)
+  {
+    short requested_pass = image_user ? image_user->pass : 0;
+    short requested_layer = image_user ? image_user->layer : 0;
+    short requested_view = image_user ? image_user->multi_index : 0;
+    /* There is room for 2 multiview textures. When a higher number is requested we should always
+     * target the first view slot. This is fine as multi view images aren't used together. */
+    if (requested_view < 2) {
+      requested_view = 0;
+    }
+
+    if (last_image_user.pass != requested_pass || last_image_user.layer != requested_layer ||
+        last_image_user.multi_index != requested_view) {
+
+      last_image_user.pass = requested_pass;
+      last_image_user.layer = requested_layer;
+      last_image_user.multi_index = requested_view;
+      reset_dirty_flag(true);
+    }
+  }
+
  private:
   /** \brief Set dirty flag of all texture slots to the given value. */
   void reset_dirty_flag(bool new_value)