From 7763ab3fcc1f728f35919aae2225c05b084f16c4 Mon Sep 17 00:00:00 2001
From: omar <omarcornut@gmail.com>
Date: Wed, 22 Nov 2017 12:26:50 +0100
Subject: [PATCH] Menu bar: better software clipping to handle small windows,
 in particular child window don't have the minimum constraint added in
 e9a7e73bbaacec886f9b39130428b81b7f95bf16 so we need to render clipped menus
 better.

---
 imgui.cpp        | 23 ++++++++++++++---------
 imgui_internal.h |  1 +
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/imgui.cpp b/imgui.cpp
index 2323dce02..c1361f735 100644
--- a/imgui.cpp
+++ b/imgui.cpp
@@ -4460,16 +4460,17 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
             window->DrawList->AddRectFilled(window->Pos+ImVec2(0,window->TitleBarHeight()), window->Pos+window->Size, bg_col, window_rounding, (flags & ImGuiWindowFlags_NoTitleBar) ? ImDrawCornerFlags_All : ImDrawCornerFlags_Bot);
 
             // Title bar
-            const bool is_focused = g.NavWindow && window->RootNonPopupWindow == g.NavWindow->RootNonPopupWindow;
+            const bool window_is_focused = g.NavWindow && window->RootNonPopupWindow == g.NavWindow->RootNonPopupWindow;
             if (!(flags & ImGuiWindowFlags_NoTitleBar))
-                window->DrawList->AddRectFilled(title_bar_rect.GetTL(), title_bar_rect.GetBR(), GetColorU32(is_focused ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg), window_rounding, ImDrawCornerFlags_Top);
+                window->DrawList->AddRectFilled(title_bar_rect.Min, title_bar_rect.Max, GetColorU32(window_is_focused ? ImGuiCol_TitleBgActive : ImGuiCol_TitleBg), window_rounding, ImDrawCornerFlags_Top);
 
             // Menu bar
             if (flags & ImGuiWindowFlags_MenuBar)
             {
                 ImRect menu_bar_rect = window->MenuBarRect();
-                window->DrawList->AddRectFilled(menu_bar_rect.GetTL(), menu_bar_rect.GetBR(), GetColorU32(ImGuiCol_MenuBarBg), (flags & ImGuiWindowFlags_NoTitleBar) ? window_rounding : 0.0f, ImDrawCornerFlags_Top);
-                if (style.FrameBorderSize > 0.0f)
+                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, menu_bar_rect.Max, GetColorU32(ImGuiCol_MenuBarBg), (flags & ImGuiWindowFlags_NoTitleBar) ? window_rounding : 0.0f, ImDrawCornerFlags_Top);
+                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);
             }
 
@@ -9231,14 +9232,18 @@ bool ImGui::BeginMenuBar()
     if (!(window->Flags & ImGuiWindowFlags_MenuBar))
         return false;
 
-    ImGuiContext& g = *GImGui;
     IM_ASSERT(!window->DC.MenuBarAppending);
     BeginGroup(); // Save position
     PushID("##menubar");
-    ImRect rect = window->MenuBarRect();
-    rect.Max.x = ImMax(rect.Min.x, rect.Max.x - g.Style.WindowRounding);
-    PushClipRect(ImVec2(ImFloor(rect.Min.x+0.5f), ImFloor(rect.Min.y + window->WindowBorderSize + 0.5f)), ImVec2(ImFloor(rect.Max.x+0.5f), ImFloor(rect.Max.y+0.5f)), false);
-    window->DC.CursorPos = ImVec2(rect.Min.x + window->DC.MenuBarOffsetX, rect.Min.y);// + g.Style.FramePadding.y);
+    
+    // We don't clip with regular 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 don't tend to display over the lower-right rounded area, which looks particularly glitchy.
+    ImRect bar_rect = window->MenuBarRect();
+    ImRect clip_rect(ImFloor(bar_rect.Min.x + 0.5f), ImFloor(bar_rect.Min.y + window->WindowBorderSize + 0.5f), ImFloor(ImMax(bar_rect.Min.x, bar_rect.Max.x - window->WindowRounding) + 0.5f), ImFloor(bar_rect.Max.y + 0.5f));
+    clip_rect.ClipWith(window->Rect());
+    PushClipRect(clip_rect.Min, clip_rect.Max, false);
+
+    window->DC.CursorPos = ImVec2(bar_rect.Min.x + window->DC.MenuBarOffsetX, bar_rect.Min.y);// + g.Style.FramePadding.y);
     window->DC.LayoutType = ImGuiLayoutType_Horizontal;
     window->DC.MenuBarAppending = true;
     AlignTextToFramePadding();
diff --git a/imgui_internal.h b/imgui_internal.h
index e54936a5b..f155abf74 100644
--- a/imgui_internal.h
+++ b/imgui_internal.h
@@ -746,6 +746,7 @@ public:
     ImGuiID     GetID(const void* ptr);
     ImGuiID     GetIDNoKeepAlive(const char* str, const char* str_end = NULL);
 
+    // We don't use g.FontSize because the window may be != g.CurrentWidow.
     ImRect      Rect() const                            { return ImRect(Pos.x, Pos.y, Pos.x+Size.x, Pos.y+Size.y); }
     float       CalcFontSize() const                    { return GImGui->FontBaseSize * FontWindowScale; }
     float       TitleBarHeight() const                  { return (Flags & ImGuiWindowFlags_NoTitleBar) ? 0.0f : CalcFontSize() + GImGui->Style.FramePadding.y * 2.0f; }