Window: Fixed one case where auto-resize by double-clicking the resize grip would make either scrollbar appear for a single frame after the resize. Moved Scrollbar visibility block.

docs/CHANGELOG.txt

@@ -42,6 +42,8 @@ Other Changes:
   will always allow submitting a 100x100 item without creating a scrollbar, regarding of WindowPadding.
   The exact meaning of ContentSize for decorated windows was previously ill-defined.
 - Window: Fixed auto-resize with AlwaysVerticalScrollbar or AlwaysHorizontalScrollbar flags.
+- Window: Fixed one case where auto-resize by double-clicking the resize grip would make either scrollbar
+  appear for a single frame after the resize.
 - Columns: Fixed Separator from creating an extraneous draw command. (#125)
 - Columns: Fixed Selectable with SpanAllColumns flag from creating an extraneous draw command. (#125)
 - Separator: Revert 1.70 "Declare its thickness (1.0f) to the layout" change. It's not incorrect

imgui.cpp

@@ -1077,7 +1077,7 @@ static int              FindWindowFocusIndex(ImGuiWindow* window);
 // Misc
 static void             UpdateMouseInputs();
 static void             UpdateMouseWheel();
-static void             UpdateManualResize(ImGuiWindow* window, const ImVec2& size_auto_fit, int* border_held, int resize_grip_count, ImU32 resize_grip_col[4]);
+static bool             UpdateManualResize(ImGuiWindow* window, const ImVec2& size_auto_fit, int* border_held, int resize_grip_count, ImU32 resize_grip_col[4]);
 static void             RenderWindowOuterBorders(ImGuiWindow* window);
 static void             RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar_rect, bool title_bar_is_highlight, int resize_grip_count, const ImU32 resize_grip_col[4], float resize_grip_draw_size);
 static void             RenderWindowTitleBarContents(ImGuiWindow* window, const ImRect& title_bar_rect, const char* name, bool* p_open);
@@ -4829,15 +4829,18 @@ static ImRect GetResizeBorderRect(ImGuiWindow* window, int border_n, float perp_
 }
 
 // Handle resize for: Resize Grips, Borders, Gamepad
-static void ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_auto_fit, int* border_held, int resize_grip_count, ImU32 resize_grip_col[4])
+// Return true when using auto-fit (double click on resize grip)
+static bool ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_auto_fit, int* border_held, int resize_grip_count, ImU32 resize_grip_col[4])
 {
     ImGuiContext& g = *GImGui;
     ImGuiWindowFlags flags = window->Flags;
+
     if ((flags & ImGuiWindowFlags_NoResize) || (flags & ImGuiWindowFlags_AlwaysAutoResize) || window->AutoFitFramesX > 0 || window->AutoFitFramesY > 0)
-        return;
+        return false;
     if (window->WasActive == false) // Early out to avoid running this code for e.g. an hidden implicit/fallback Debug window.
-        return;
+        return false;
 
+    bool ret_auto_fit = false;
     const int resize_border_count = g.IO.ConfigWindowsResizeFromEdges ? 4 : 0;
     const float grip_draw_size = (float)(int)ImMax(g.FontSize * 1.35f, window->WindowRounding + 1.0f + g.FontSize * 0.2f);
     const float grip_hover_inner_size = (float)(int)(grip_draw_size * 0.75f);
@@ -4871,6 +4874,7 @@ static void ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_au
         {
             // Manual auto-fit when double-clicking
             size_target = CalcSizeAfterConstraint(window, size_auto_fit);
+            ret_auto_fit = true;
             ClearActiveID();
         }
         else if (held)
@@ -4945,6 +4949,7 @@ static void ImGui::UpdateManualResize(ImGuiWindow* window, const ImVec2& size_au
     window->DC.NavLayerCurrentMask = (1 << ImGuiNavLayer_Main);
 
     window->Size = window->SizeFull;
+    return ret_auto_fit;
 }
 
 static inline void ClampWindowRect(ImGuiWindow* window, const ImRect& rect, const ImVec2& padding)
@@ -5478,7 +5483,8 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
         const int resize_grip_count = g.IO.ConfigWindowsResizeFromEdges ? 2 : 1; // 4
         const float resize_grip_draw_size = (float)(int)ImMax(g.FontSize * 1.35f, window->WindowRounding + 1.0f + g.FontSize * 0.2f);
         if (!window->Collapsed)
-            UpdateManualResize(window, size_auto_fit, &border_held, resize_grip_count, &resize_grip_col[0]);
+            if (UpdateManualResize(window, size_auto_fit, &border_held, resize_grip_count, &resize_grip_col[0]))
+                use_current_size_for_scrollbar_x = use_current_size_for_scrollbar_y = true;
         window->ResizeBorderHeld = (signed char)border_held;
 
         // SCROLLBAR VISIBILITY