Windows, Style: Fixed small rendering issues with menu bar, resize grip and scrollbar when using thick border sizes. (#8267, #7887)

Amend e.g. 742b5f4c.

docs/CHANGELOG.txt

@@ -67,6 +67,8 @@ Other changes:
 - Windows: legacy SetWindowFontScale() is properly inherited by nested child
   windows. Note that an upcoming major release should make this obsolete,
   but in the meanwhile it works better now. (#2701, #8138, #1018)
+- Windows, Style: Fixed small rendering issues with menu bar, resize grip and
+  scrollbar when using thick border sizes. (#8267, #7887)
 - ColorEdit, ColorPicker: Fixed alpha preview broken in 1.91.7. (#8336, #8241). [@PathogenDavid]
 - Tabs, Style: reworked selected overline rendering to better accommodate
   for rounded tabs. Reduced default thickness (style.TabBarOverlineSize),

imgui.cpp

@@ -6712,7 +6712,7 @@ static void ImGui::RenderWindowOuterBorders(ImGuiWindow* window)
     if (g.Style.FrameBorderSize > 0 && !(window->Flags & ImGuiWindowFlags_NoTitleBar))
     {
         float y = window->Pos.y + window->TitleBarHeight - 1;
-        window->DrawList->AddLine(ImVec2(window->Pos.x + border_size, y), ImVec2(window->Pos.x + window->Size.x - border_size, y), border_col, g.Style.FrameBorderSize);
+        window->DrawList->AddLine(ImVec2(window->Pos.x + border_size * 0.5f, y), ImVec2(window->Pos.x + window->Size.x - border_size * 0.5f, y), border_col, g.Style.FrameBorderSize);
     }
 }
 
@@ -6772,9 +6772,10 @@ void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar
         {
             ImRect menu_bar_rect = window->MenuBarRect();
             menu_bar_rect.ClipWith(window->Rect());  // Soft clipping, in particular child window don't have minimum size covering the menu bar so this is useful for them.
-            window->DrawList->AddRectFilled(menu_bar_rect.Min + ImVec2(window_border_size, 0), menu_bar_rect.Max - ImVec2(window_border_size, 0), GetColorU32(ImGuiCol_MenuBarBg), (flags & ImGuiWindowFlags_NoTitleBar) ? window_rounding : 0.0f, ImDrawFlags_RoundCornersTop);
+            window->DrawList->AddRectFilled(menu_bar_rect.Min, menu_bar_rect.Max, GetColorU32(ImGuiCol_MenuBarBg), (flags & ImGuiWindowFlags_NoTitleBar) ? window_rounding : 0.0f, ImDrawFlags_RoundCornersTop);
+            float window_border_size = window->WindowBorderSize;
             if (style.FrameBorderSize > 0.0f && menu_bar_rect.Max.y < window->Pos.y + window->Size.y)
-                window->DrawList->AddLine(menu_bar_rect.GetBL(), menu_bar_rect.GetBR(), GetColorU32(ImGuiCol_Border), style.FrameBorderSize);
+                window->DrawList->AddLine(menu_bar_rect.GetBL() + ImVec2(window_border_size * 0.5f, 0.0f), menu_bar_rect.GetBR() - ImVec2(window_border_size * 0.5f, 0.0f), GetColorU32(ImGuiCol_Border), style.FrameBorderSize);
         }
 
         // Scrollbars
@@ -6793,9 +6794,10 @@ void ImGui::RenderWindowDecorations(ImGuiWindow* window, const ImRect& title_bar
                     continue;
                 const ImGuiResizeGripDef& grip = resize_grip_def[resize_grip_n];
                 const ImVec2 corner = ImLerp(window->Pos, window->Pos + window->Size, grip.CornerPosN);
-                window->DrawList->PathLineTo(corner + grip.InnerDir * ((resize_grip_n & 1) ? ImVec2(window_border_size, resize_grip_draw_size) : ImVec2(resize_grip_draw_size, window_border_size)));
-                window->DrawList->PathLineTo(corner + grip.InnerDir * ((resize_grip_n & 1) ? ImVec2(resize_grip_draw_size, window_border_size) : ImVec2(window_border_size, resize_grip_draw_size)));
-                window->DrawList->PathArcToFast(ImVec2(corner.x + grip.InnerDir.x * (window_rounding + window_border_size), corner.y + grip.InnerDir.y * (window_rounding + window_border_size)), window_rounding, grip.AngleMin12, grip.AngleMax12);
+                const float border_inner = IM_ROUND(window_border_size * 0.5f);
+                window->DrawList->PathLineTo(corner + grip.InnerDir * ((resize_grip_n & 1) ? ImVec2(border_inner, resize_grip_draw_size) : ImVec2(resize_grip_draw_size, border_inner)));
+                window->DrawList->PathLineTo(corner + grip.InnerDir * ((resize_grip_n & 1) ? ImVec2(resize_grip_draw_size, border_inner) : ImVec2(border_inner, resize_grip_draw_size)));
+                window->DrawList->PathArcToFast(ImVec2(corner.x + grip.InnerDir.x * (window_rounding + border_inner), corner.y + grip.InnerDir.y * (window_rounding + border_inner)), window_rounding, grip.AngleMin12, grip.AngleMax12);
                 window->DrawList->PathFillConvex(col);
             }
         }

imgui_widgets.cpp

@@ -911,13 +911,14 @@ ImRect ImGui::GetWindowScrollbarRect(ImGuiWindow* window, ImGuiAxis axis)
 {
     const ImRect outer_rect = window->Rect();
     const ImRect inner_rect = window->InnerRect;
-    const float border_size = window->WindowBorderSize;
     const float scrollbar_size = window->ScrollbarSizes[axis ^ 1]; // (ScrollbarSizes.x = width of Y scrollbar; ScrollbarSizes.y = height of X scrollbar)
     IM_ASSERT(scrollbar_size > 0.0f);
+    const float border_size = IM_ROUND(window->WindowBorderSize * 0.5f);
+    const float border_top = (window->Flags & ImGuiWindowFlags_MenuBar) ? IM_ROUND(GImGui->Style.FrameBorderSize * 0.5f) : 0.0f;
     if (axis == ImGuiAxis_X)
-        return ImRect(inner_rect.Min.x, ImMax(outer_rect.Min.y, outer_rect.Max.y - border_size - scrollbar_size), inner_rect.Max.x - border_size, outer_rect.Max.y - border_size);
+        return ImRect(inner_rect.Min.x + border_size, ImMax(outer_rect.Min.y + border_size, outer_rect.Max.y - border_size - scrollbar_size), inner_rect.Max.x - border_size, outer_rect.Max.y - border_size);
     else
-        return ImRect(ImMax(outer_rect.Min.x, outer_rect.Max.x - border_size - scrollbar_size), inner_rect.Min.y, outer_rect.Max.x - border_size, inner_rect.Max.y - border_size);
+        return ImRect(ImMax(outer_rect.Min.x, outer_rect.Max.x - border_size - scrollbar_size), inner_rect.Min.y + border_top, outer_rect.Max.x - border_size, inner_rect.Max.y - border_size);
 }
 
 void ImGui::Scrollbar(ImGuiAxis axis)
@@ -8630,8 +8631,9 @@ bool ImGui::BeginMenuBar()
 
     // We don't clip with current window clipping rectangle as it is already set to the area below. However we clip with window full rect.
     // We remove 1 worth of rounding to Max.x to that text in long menus and small windows don't tend to display over the lower-right rounded area, which looks particularly glitchy.
+    const float border_top = ImMax(window->WindowBorderSize * 0.5f - window->TitleBarHeight, 0.0f);
     ImRect bar_rect = window->MenuBarRect();
-    ImRect clip_rect(IM_ROUND(bar_rect.Min.x + window->WindowBorderSize), IM_ROUND(bar_rect.Min.y + window->WindowBorderSize), IM_ROUND(ImMax(bar_rect.Min.x, bar_rect.Max.x - ImMax(window->WindowRounding, window->WindowBorderSize))), IM_ROUND(bar_rect.Max.y));
+    ImRect clip_rect(IM_ROUND(bar_rect.Min.x + window->WindowBorderSize * 0.5f), IM_ROUND(bar_rect.Min.y + border_top), IM_ROUND(ImMax(bar_rect.Min.x, bar_rect.Max.x - ImMax(window->WindowRounding, window->WindowBorderSize * 0.5f))), IM_ROUND(bar_rect.Max.y));
     clip_rect.ClipWith(window->OuterRectClipped);
     PushClipRect(clip_rect.Min, clip_rect.Max, false);