Bug 1539998 [Linux] Implement nsLookAndFeel::GetTitlebarAction() r=emilio

Get titlebar actions from gtk-titlebar-double-click / gtk-titlebar-middle-click gsettings keys and monitor key changes and export it as nsLookAndFeel::GetTitlebarAction().

Differential Revision: https://phabricator.services.mozilla.com/D199882

widget/LookAndFeel.h

@@ -493,6 +493,28 @@ class LookAndFeel {
    */
   static bool DrawInTitlebar();
 
+  enum class TitlebarAction {
+    None,
+    WindowLower,
+    WindowMenu,
+    WindowMinimize,
+    WindowMaximize,
+    WindowMaximizeToggle,
+    // We don't support more actions (maximize-horizontal, maximize-vertical,..)
+    // as they're implemented as part of Wayland gtk_surface1 protocol
+    // which is not accessible to us.
+  };
+
+  enum class TitlebarEvent {
+    Double_Click,
+    Middle_Click,
+  };
+
+  /**
+   * Get system defined action for titlebar events.
+   */
+  static TitlebarAction GetTitlebarAction(TitlebarEvent aEvent);
+
   /**
    * The millisecond to mask password value.
    * This value is only valid when GetEchoPassword() returns true.

widget/gtk/nsLookAndFeel.cpp

@@ -189,6 +189,9 @@ nsLookAndFeel::nsLookAndFeel() {
       "notify::gtk-menu-popup-delay"_ns,
       // Affects DragThresholdX/Y
       "notify::gtk-dnd-drag-threshold"_ns,
+      // Affects titlebar actions loaded at moz_gtk_refresh().
+      "notify::gtk-titlebar-double-click"_ns,
+      "notify::gtk-titlebar-middle-click"_ns,
   };
 
   GtkSettings* settings = gtk_settings_get_default();
@@ -1620,6 +1623,36 @@ void nsLookAndFeel::InitializeGlobalSettings() {
       *pos = i;
     }
   }
+
+  struct actionMapping {
+    TitlebarAction action;
+    char name[100];
+  } ActionMapping[] = {
+      {TitlebarAction::None, "none"},
+      {TitlebarAction::WindowLower, "lower"},
+      {TitlebarAction::WindowMenu, "menu"},
+      {TitlebarAction::WindowMinimize, "minimize"},
+      {TitlebarAction::WindowMaximize, "maximize"},
+      {TitlebarAction::WindowMaximizeToggle, "toggle-maximize"},
+  };
+
+  auto GetWindowAction = [&](const char* eventName) -> TitlebarAction {
+    gchar* action = nullptr;
+    g_object_get(settings, eventName, &action, nullptr);
+    if (!action) {
+      return TitlebarAction::None;
+    }
+    auto free = mozilla::MakeScopeExit([&] { g_free(action); });
+    for (auto const mapping : ActionMapping) {
+      if (!strncmp(action, mapping.name, strlen(mapping.name))) {
+        return mapping.action;
+      }
+    }
+    return TitlebarAction::None;
+  };
+
+  mDoubleClickAction = GetWindowAction("gtk-titlebar-double-click");
+  mMiddleClickAction = GetWindowAction("gtk-titlebar-middle-click");
 }
 
 void nsLookAndFeel::ConfigureFinalEffectiveTheme() {
@@ -2233,6 +2266,12 @@ bool nsLookAndFeel::GetEchoPasswordImpl() { return false; }
 
 bool nsLookAndFeel::GetDefaultDrawInTitlebar() { return sCSDAvailable; }
 
+nsXPLookAndFeel::TitlebarAction nsLookAndFeel::GetTitlebarAction(
+    TitlebarEvent aEvent) {
+  return aEvent == TitlebarEvent::Double_Click ? mDoubleClickAction
+                                               : mMiddleClickAction;
+}
+
 void nsLookAndFeel::GetThemeInfo(nsACString& aInfo) {
   aInfo.Append(mSystemTheme.mName);
   aInfo.Append(" / ");

widget/gtk/nsLookAndFeel.h

@@ -42,6 +42,9 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
 
   bool GetDefaultDrawInTitlebar() override;
 
+  nsXPLookAndFeel::TitlebarAction GetTitlebarAction(
+      TitlebarEvent aEvent) override;
+
   void GetThemeInfo(nsACString&) override;
 
   static const nscolor kBlack = NS_RGB(0, 0, 0);
@@ -179,6 +182,8 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
   int32_t mCSDMaximizeButtonPosition = 0;
   int32_t mCSDMinimizeButtonPosition = 0;
   int32_t mCSDCloseButtonPosition = 0;
+  TitlebarAction mDoubleClickAction = TitlebarAction::None;
+  TitlebarAction mMiddleClickAction = TitlebarAction::None;
 
   RefPtr<GtkCssProvider> mRoundedCornerProvider;
   void UpdateRoundedBottomCornerStyles();

widget/nsXPLookAndFeel.cpp

@@ -1495,6 +1495,11 @@ bool LookAndFeel::DrawInTitlebar() {
   return nsLookAndFeel::GetInstance()->GetDefaultDrawInTitlebar();
 }
 
+LookAndFeel::TitlebarAction LookAndFeel::GetTitlebarAction(
+    TitlebarEvent aEvent) {
+  return nsLookAndFeel::GetInstance()->GetTitlebarAction(aEvent);
+}
+
 void LookAndFeel::GetThemeInfo(nsACString& aOut) {
   nsLookAndFeel::GetInstance()->GetThemeInfo(aOut);
 }

widget/nsXPLookAndFeel.h

@@ -57,6 +57,10 @@ class nsXPLookAndFeel : public mozilla::LookAndFeel {
 
   virtual bool GetDefaultDrawInTitlebar() { return true; }
 
+  virtual TitlebarAction GetTitlebarAction(TitlebarEvent aEvent) {
+    return TitlebarAction::None;
+  }
+
   static bool LookAndFeelFontToStyle(const LookAndFeelFont&, nsString& aName,
                                      gfxFontStyle&);
   static LookAndFeelFont StyleToLookAndFeelFont(const nsAString& aName,