[gnome-builder] libide/sourceview: implement ctrl+scroll for zoom

[Christian Hergert <chergert src gnome org>]

commit 8a68ee2259e5dab79bc7bf59d8e313741f058bad
Author: Christian Hergert <chergert redhat com>
Date:   Wed Jul 20 22:30:59 2022 -0700

    libide/sourceview: implement ctrl+scroll for zoom

 src/libide/sourceview/ide-source-view.c | 49 +++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
---
diff --git a/src/libide/sourceview/ide-source-view.c b/src/libide/sourceview/ide-source-view.c
index 17348ce0e..642977010 100644
--- a/src/libide/sourceview/ide-source-view.c
+++ b/src/libide/sourceview/ide-source-view.c
@@ -573,6 +573,45 @@ ide_source_view_zoom_one_action (GtkWidget  *widget,
   ide_source_view_set_font_scale (self, 1);
 }
 
+static void
+ide_source_view_zoom (IdeSourceView *self,
+                      int            amount)
+{
+  g_assert (IDE_IS_SOURCE_VIEW (self));
+
+  if (amount == 0)
+    self->font_scale = 0;
+  else
+    self->font_scale += amount;
+
+  ide_source_view_update_css (self);
+
+  g_object_notify_by_pspec (G_OBJECT (self), properties [PROP_FONT_SCALE]);
+  g_object_notify_by_pspec (G_OBJECT (self), properties [PROP_ZOOM_LEVEL]);
+}
+
+static gboolean
+on_scroll_scrolled_cb (GtkEventControllerScroll *scroll,
+                       double                    dx,
+                       double                    dy,
+                       IdeSourceView            *self)
+{
+  GdkModifierType mods;
+
+  g_assert (GTK_IS_EVENT_CONTROLLER_SCROLL (scroll));
+  g_assert (IDE_IS_SOURCE_VIEW (self));
+
+  mods = gtk_event_controller_get_current_event_state (GTK_EVENT_CONTROLLER (scroll));
+
+  if ((mods & GDK_CONTROL_MASK) != 0)
+    {
+      ide_source_view_zoom (self, dy < 0 ? 1 : -1);
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
 static void
 ide_source_view_push_snippet (GtkSourceView    *source_view,
                               GtkSourceSnippet *snippet,
@@ -796,6 +835,7 @@ ide_source_view_init (IdeSourceView *self)
   GtkStyleContext *style_context;
   GtkEventController *click;
   GtkEventController *focus;
+  GtkEventController *scroll;
 
   g_signal_connect (self,
                     "notify::buffer",
@@ -832,6 +872,15 @@ ide_source_view_init (IdeSourceView *self)
                             self);
   gtk_widget_add_controller (GTK_WIDGET (self), focus);
 
+  /* Setup ctrl+scroll zoom */
+  scroll = gtk_event_controller_scroll_new (GTK_EVENT_CONTROLLER_SCROLL_VERTICAL);
+  gtk_event_controller_set_propagation_phase (scroll, GTK_PHASE_CAPTURE);
+  g_signal_connect (scroll,
+                    "scroll",
+                    G_CALLBACK (on_scroll_scrolled_cb),
+                    self);
+  gtk_widget_add_controller (GTK_WIDGET (self), scroll);
+
   /* This is sort of a layer vioaltion, but it's helpful for us to
    * get the system font name and manage it invisibly.
    */