From 4ef6cbf4fb6f414cca79e3082995ad4d6504362c Mon Sep 17 00:00:00 2001
From: Ian McInerney <ian.s.mcinerney@ieee.org>
Date: Wed, 12 Apr 2023 15:22:04 +0100
Subject: [PATCH] Add hack to speed up font choice box widget creation

There are problems internal to GTK that mean creating choice boxes with
a lot of items is a very slow process. This hack works around one of
those issues to make it faster to create and display the menu in the
choice box.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/14277

(Cherry-picked from a77e94d16fc6de0b3bbbc30bba7b46bd1bf0ad83)
---
 common/widgets/font_choice.cpp          |  5 ++++
 libs/kiplatform/gtk/ui.cpp              | 39 +++++++++++++++++++++++++
 libs/kiplatform/include/kiplatform/ui.h |  8 +++++
 libs/kiplatform/msw/ui.cpp              |  6 ++++
 libs/kiplatform/osx/ui.mm               |  6 ++++
 5 files changed, 64 insertions(+)

diff --git a/common/widgets/font_choice.cpp b/common/widgets/font_choice.cpp
index 42db88c345..c295cb2446 100644
--- a/common/widgets/font_choice.cpp
+++ b/common/widgets/font_choice.cpp
@@ -18,6 +18,7 @@
  */
 
 #include <widgets/font_choice.h>
+#include <kiplatform/ui.h>
 #include <wx/fontenum.h>
 #include <font/fontconfig.h>
 #include <pgm_base.h>
@@ -54,7 +55,11 @@ FONT_CHOICE::FONT_CHOICE( wxWindow* aParent, int aId, wxPoint aPosition, wxSize
         menuList.Add( wxString( name ) );
 
     menuList.Sort();
+
+    Freeze();
     Append( menuList );
+    KIPLATFORM::UI::LargeChoiceBoxHack( this );
+    Thaw();
 
     m_notFound = wxS( " " ) + _( "<not found>" );
 }
diff --git a/libs/kiplatform/gtk/ui.cpp b/libs/kiplatform/gtk/ui.cpp
index 8bfc554844..b47e2acd4c 100644
--- a/libs/kiplatform/gtk/ui.cpp
+++ b/libs/kiplatform/gtk/ui.cpp
@@ -89,6 +89,45 @@ bool KIPLATFORM::UI::IsStockCursorOk( wxStockCursor aCursor )
 }
 
 
+/**
+ * The following two functions are based on the "hack" contained in the attached patch at
+ * https://gitlab.gnome.org/GNOME/gtk/-/issues/1910 which is supposed to speed up creation of
+ * GTK choice boxes.
+ *
+ * The basic idea is to disable some of the event handlers on the menus for the choice box to
+ * prevent them from running, which will speed up the creation of the choice box and its popup menu.
+ */
+static void disable_area_apply_attributes_cb( GtkWidget* pItem, gpointer userdata )
+{
+    // GTK needs this enormous chain to get the actual type of item that we want
+    GtkMenuItem*   pMenuItem   = GTK_MENU_ITEM( pItem );
+    GtkWidget*     child       = gtk_bin_get_child( GTK_BIN( pMenuItem ) );
+    GtkCellView*   pCellView   = GTK_CELL_VIEW( child );
+    GtkCellLayout* pCellLayout = GTK_CELL_LAYOUT( pCellView );
+    GtkCellArea*   pCellArea   = gtk_cell_layout_get_area( pCellLayout );
+
+    g_signal_handlers_block_matched( pCellArea, G_SIGNAL_MATCH_DATA, 0, 0, NULL, NULL, userdata );
+}
+
+
+void KIPLATFORM::UI::LargeChoiceBoxHack( wxChoice* aChoice )
+{
+    AtkObject* atkObj = gtk_combo_box_get_popup_accessible( GTK_COMBO_BOX( aChoice->m_widget ) );
+
+    if( !atkObj || !GTK_IS_ACCESSIBLE( atkObj ) )
+        return;
+
+    GtkWidget* widget = gtk_accessible_get_widget( GTK_ACCESSIBLE( atkObj ) );
+
+    if( !widget || !GTK_IS_MENU( widget ) )
+        return;
+
+    GtkMenu* menu = GTK_MENU( widget );
+
+    gtk_container_foreach( GTK_CONTAINER( menu ), disable_area_apply_attributes_cb, menu );
+}
+
+
 void KIPLATFORM::UI::EllipsizeChoiceBox( wxChoice* aChoice )
 {
     // This function is based on the code inside the function post_process_ui in
diff --git a/libs/kiplatform/include/kiplatform/ui.h b/libs/kiplatform/include/kiplatform/ui.h
index 23b5571c02..490e513787 100644
--- a/libs/kiplatform/include/kiplatform/ui.h
+++ b/libs/kiplatform/include/kiplatform/ui.h
@@ -86,6 +86,14 @@ namespace KIPLATFORM
          */
         bool IsStockCursorOk( wxStockCursor aCursor );
 
+        /**
+         * Configure a wxChoice control to support a lot of entries by disabling functionality that makes
+         * adding new items become very expensive.
+         *
+         * @param aChoice is the choice box to modify
+         */
+        void LargeChoiceBoxHack( wxChoice* aChoice );
+
         /**
          * Configure a wxChoice control to ellipsize the shown text in the button with the ellipses
          * placed at the end of the string.
diff --git a/libs/kiplatform/msw/ui.cpp b/libs/kiplatform/msw/ui.cpp
index 02bd03f6ee..733c9fd7d4 100644
--- a/libs/kiplatform/msw/ui.cpp
+++ b/libs/kiplatform/msw/ui.cpp
@@ -110,6 +110,12 @@ bool KIPLATFORM::UI::IsStockCursorOk( wxStockCursor aCursor )
 }
 
 
+void KIPLATFORM::UI::LargeChoiceBoxHack( wxChoice* aChoice )
+{
+    // Not implemented
+}
+
+
 void KIPLATFORM::UI::EllipsizeChoiceBox( wxChoice* aChoice )
 {
     // Not implemented
diff --git a/libs/kiplatform/osx/ui.mm b/libs/kiplatform/osx/ui.mm
index 2e7e461fc5..807a0bb1be 100644
--- a/libs/kiplatform/osx/ui.mm
+++ b/libs/kiplatform/osx/ui.mm
@@ -109,6 +109,12 @@ bool KIPLATFORM::UI::IsStockCursorOk( wxStockCursor aCursor )
 }
 
 
+void KIPLATFORM::UI::LargeChoiceBoxHack( wxChoice* aChoice )
+{
+    // Not implemented
+}
+
+
 void KIPLATFORM::UI::EllipsizeChoiceBox( wxChoice* aChoice )
 {
     // Not implemented