Texutres: minor comments, tweaks.

imgui_draw.cpp

@@ -2740,10 +2740,9 @@ void ImFontAtlasUpdateNewFrame(ImFontAtlas* atlas, int frame_count, bool rendere
         if (atlas->Builder == NULL) // This will only happen if fonts were not already loaded.
             ImFontAtlasBuildMain(atlas);
     }
-    else // Legacy backend
-    {
+    // Legacy backend
+    if (!atlas->RendererHasTextures)
         IM_ASSERT_USER_ERROR(atlas->TexIsBuilt, "Backend does not support ImGuiBackendFlags_RendererHasTextures, and font atlas is not built! Update backend OR make sure you called ImGui_ImplXXXX_NewFrame() function for renderer backend, which should call io.Fonts->GetTexDataAsRGBA32() / GetTexDataAsAlpha8().");
-    }
     if (atlas->TexIsBuilt && atlas->Builder->PreloadedAllGlyphsRanges)
         IM_ASSERT_USER_ERROR(atlas->RendererHasTextures == false, "Called ImFontAtlas::Build() before ImGuiBackendFlags_RendererHasTextures got set! With new backends: you don't need to call Build().");
 
@@ -2798,8 +2797,9 @@ void ImFontAtlasUpdateNewFrame(ImFontAtlas* atlas, int frame_count, bool rendere
         }
         else if (tex->WantDestroyNextFrame && tex->Status != ImTextureStatus_WantDestroy)
         {
-            // Request destroy. Keep bool as it allows us to keep track of things.
-            // We don't destroy pixels right away, as backend may have an in-flight copy from RAM.
+            // Request destroy.
+            // - Keep bool to true in order to differentiate a planned destroy vs a destroy decided by the backend.
+            // - We don't destroy pixels right away, as backend may have an in-flight copy from RAM.
             IM_ASSERT(tex->Status == ImTextureStatus_OK || tex->Status == ImTextureStatus_WantCreate || tex->Status == ImTextureStatus_WantUpdates);
             tex->Status = ImTextureStatus_WantDestroy;
         }
@@ -2955,7 +2955,7 @@ void ImFontAtlasTextureBlockQueueUpload(ImFontAtlas* atlas, ImTextureData* tex,
     tex->UsedRect.h = (unsigned short)(ImMax(tex->UsedRect.y + tex->UsedRect.h, req.y + req.h) - tex->UsedRect.y);
     atlas->TexIsBuilt = false;
 
-    // No need to queue if status is _WantCreate
+    // No need to queue if status is == ImTextureStatus_WantCreate
     if (tex->Status == ImTextureStatus_OK || tex->Status == ImTextureStatus_WantUpdates)
     {
         tex->Status = ImTextureStatus_WantUpdates;