Internals: Moved scrollbar visibility calculation block below the call to UpdateManualResize(). This commit is _intended_ to have no side-effect (next commit will). Also moved ItemWidthDefault calculation below rectangles.

imgui.cpp

@@ -5416,26 +5416,6 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         // Decoration size
         const float decoration_up_height = window->TitleBarHeight() + window->MenuBarHeight();
 
-        // SCROLLBAR VISIBILITY
-
-        // Update scrollbar visibility (based on the Size that was effective during last frame or the auto-resized Size).
-        if (!window->Collapsed)
-        {
-            // When reading the current size we need to read it after size constraints have been applied.
-            // When we use InnerRect here we are intentionally reading last frame size, same for ScrollbarSizes values before we set them again.
-            ImVec2 avail_size_from_current_frame = ImVec2(window->SizeFull.x, window->SizeFull.y - decoration_up_height);
-            ImVec2 avail_size_from_last_frame = window->InnerRect.GetSize() + window->ScrollbarSizes;
-            ImVec2 needed_size_from_last_frame = window_just_created ? ImVec2(0, 0) : window->ContentSize + window->WindowPadding * 2.0f;
-            float size_x_for_scrollbars = use_current_size_for_scrollbar_x ? avail_size_from_current_frame.x : avail_size_from_last_frame.x;
-            float size_y_for_scrollbars = use_current_size_for_scrollbar_y ? avail_size_from_current_frame.y : avail_size_from_last_frame.y;
-            //bool scrollbar_y_from_last_frame = window->ScrollbarY; // FIXME: May want to use that in the ScrollbarX expression? How many pros vs cons?
-            window->ScrollbarY = (flags & ImGuiWindowFlags_AlwaysVerticalScrollbar) || ((needed_size_from_last_frame.y > size_y_for_scrollbars) && !(flags & ImGuiWindowFlags_NoScrollbar));
-            window->ScrollbarX = (flags & ImGuiWindowFlags_AlwaysHorizontalScrollbar) || ((needed_size_from_last_frame.x > size_x_for_scrollbars - (window->ScrollbarY ? style.ScrollbarSize : 0.0f)) && !(flags & ImGuiWindowFlags_NoScrollbar) && (flags & ImGuiWindowFlags_HorizontalScrollbar));
-            if (window->ScrollbarX && !window->ScrollbarY)
-                window->ScrollbarY = (needed_size_from_last_frame.y > size_y_for_scrollbars) && !(flags & ImGuiWindowFlags_NoScrollbar);
-            window->ScrollbarSizes = ImVec2(window->ScrollbarY ? style.ScrollbarSize : 0.0f, window->ScrollbarX ? style.ScrollbarSize : 0.0f);
-        }
-
         // POSITION
 
         // Popup latch its initial position, will position itself when it appears next frame
@@ -5466,7 +5446,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         else if ((flags & ImGuiWindowFlags_Tooltip) != 0 && !window_pos_set_by_api && !window_is_child_tooltip)
             window->Pos = FindBestWindowPosForPopup(window);
 
-        // Clamp position so it stays visible
+        // Clamp position/size so it stays visible
         // Ignore zero-sized display explicitly to avoid losing positions if a window manager reports zero-sized window when initializing or minimizing.
         ImRect viewport_rect(GetViewportRect());
         if (!window_pos_set_by_api && !(flags & ImGuiWindowFlags_ChildWindow) && window->AutoFitFramesX <= 0 && window->AutoFitFramesY <= 0)
@@ -5501,11 +5481,25 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             UpdateManualResize(window, size_auto_fit, &border_held, resize_grip_count, &resize_grip_col[0]);
         window->ResizeBorderHeld = (signed char)border_held;
 
-        // Default item width. Make it proportional to window size if window manually resizes
-        if (window->Size.x > 0.0f && !(flags & ImGuiWindowFlags_Tooltip) && !(flags & ImGuiWindowFlags_AlwaysAutoResize))
-            window->ItemWidthDefault = (float)(int)(window->Size.x * 0.65f);
-        else
-            window->ItemWidthDefault = (float)(int)(g.FontSize * 16.0f);
+        // SCROLLBAR VISIBILITY
+
+        // Update scrollbar visibility (based on the Size that was effective during last frame or the auto-resized Size).
+        if (!window->Collapsed)
+        {
+            // When reading the current size we need to read it after size constraints have been applied.
+            // When we use InnerRect here we are intentionally reading last frame size, same for ScrollbarSizes values before we set them again.
+            ImVec2 avail_size_from_current_frame = ImVec2(window->SizeFull.x, window->SizeFull.y - decoration_up_height);
+            ImVec2 avail_size_from_last_frame = window->InnerRect.GetSize() + window->ScrollbarSizes;
+            ImVec2 needed_size_from_last_frame = window_just_created ? ImVec2(0, 0) : window->ContentSize + window->WindowPadding * 2.0f;
+            float size_x_for_scrollbars = use_current_size_for_scrollbar_x ? avail_size_from_current_frame.x : avail_size_from_last_frame.x;
+            float size_y_for_scrollbars = use_current_size_for_scrollbar_y ? avail_size_from_current_frame.y : avail_size_from_last_frame.y;
+            //bool scrollbar_y_from_last_frame = window->ScrollbarY; // FIXME: May want to use that in the ScrollbarX expression? How many pros vs cons?
+            window->ScrollbarY = (flags & ImGuiWindowFlags_AlwaysVerticalScrollbar) || ((needed_size_from_last_frame.y > size_y_for_scrollbars) && !(flags & ImGuiWindowFlags_NoScrollbar));
+            window->ScrollbarX = (flags & ImGuiWindowFlags_AlwaysHorizontalScrollbar) || ((needed_size_from_last_frame.x > size_x_for_scrollbars - (window->ScrollbarY ? style.ScrollbarSize : 0.0f)) && !(flags & ImGuiWindowFlags_NoScrollbar) && (flags & ImGuiWindowFlags_HorizontalScrollbar));
+            if (window->ScrollbarX && !window->ScrollbarY)
+                window->ScrollbarY = (needed_size_from_last_frame.y > size_y_for_scrollbars) && !(flags & ImGuiWindowFlags_NoScrollbar);
+            window->ScrollbarSizes = ImVec2(window->ScrollbarY ? style.ScrollbarSize : 0.0f, window->ScrollbarX ? style.ScrollbarSize : 0.0f);
+        }
 
         // UPDATE RECTANGLES (1- THOSE NOT AFFECTED BY SCROLLING)
         // Update various regions. Variables they depends on should be set above in this function.
@@ -5547,6 +5541,12 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         window->InnerClipRect.Max.y = ImFloor(0.5f + window->InnerRect.Max.y - window->WindowBorderSize);
         window->InnerClipRect.ClipWithFull(host_rect);
 
+        // Default item width. Make it proportional to window size if window manually resizes
+        if (window->Size.x > 0.0f && !(flags & ImGuiWindowFlags_Tooltip) && !(flags & ImGuiWindowFlags_AlwaysAutoResize))
+            window->ItemWidthDefault = (float)(int)(window->Size.x * 0.65f);
+        else
+            window->ItemWidthDefault = (float)(int)(g.FontSize * 16.0f);
+
         // SCROLLING
 
         // Lock down maximum scrolling