[virt-tools-list] [PATCH virt-viewer v3] virt-viewer-window: Change zoom of the display only when it is possible

[Pavel Grunt]

Do not allow to zoom out if it is not possible due to the width of
the top menu. It avoids emitting size allocation events that will
change the display resolution of the spice guest.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1206460
---
v3:
 - return when zoom level doesn't change
 - more comments
v2:
 - treatment of zoom level moved to _window_set_zoom_level() in order to make it work in all cases (ie. with the command line option '-z')
 - _get_minimal_zoom_level() instead of _can_zoom_out()
 - more debug logs
---
 src/virt-viewer-window.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 71 insertions(+), 1 deletion(-)

diff --git a/src/virt-viewer-window.c b/src/virt-viewer-window.c
index 799adce..75966c3 100644
--- a/src/virt-viewer-window.c
+++ b/src/virt-viewer-window.c
@@ -34,9 +34,11 @@
 #include <locale.h>
 #include <glib/gprintf.h>
 #include <glib/gi18n.h>
+#include <math.h>
 
 #include "virt-gtk-compat.h"
 #include "virt-viewer-window.h"
+#include "virt-viewer-display.h"
 #include "virt-viewer-session.h"
 #include "virt-viewer-app.h"
 #include "virt-viewer-util.h"
@@ -67,6 +69,8 @@ static void virt_viewer_window_disable_modifiers(VirtViewerWindow *self);
 static void virt_viewer_window_resize(VirtViewerWindow *self, gboolean keep_win_size);
 static void virt_viewer_window_toolbar_setup(VirtViewerWindow *self);
 static GtkMenu* virt_viewer_window_get_keycombo_menu(VirtViewerWindow *self);
+static void virt_viewer_window_get_minimal_dimensions(VirtViewerWindow *self, guint *width, guint *height);
+static gint virt_viewer_window_get_minimal_zoom_level(VirtViewerWindow *self);
 
 G_DEFINE_TYPE (VirtViewerWindow, virt_viewer_window, G_TYPE_OBJECT)
 
@@ -1306,7 +1310,7 @@ virt_viewer_window_set_display(VirtViewerWindow *self, VirtViewerDisplay *displa
     if (display != NULL) {
         priv->display = g_object_ref(display);
 
-        virt_viewer_display_set_zoom_level(VIRT_VIEWER_DISPLAY(priv->display), priv->zoomlevel);
+        virt_viewer_window_set_zoom_level(self, priv->zoomlevel);
         virt_viewer_display_set_monitor(VIRT_VIEWER_DISPLAY(priv->display), priv->fullscreen_monitor);
         virt_viewer_display_set_fullscreen(VIRT_VIEWER_DISPLAY(priv->display), priv->fullscreen);
 
@@ -1402,9 +1406,11 @@ void
 virt_viewer_window_set_zoom_level(VirtViewerWindow *self, gint zoom_level)
 {
     VirtViewerWindowPrivate *priv;
+    gint min_zoom, old_zoom;
 
     g_return_if_fail(VIRT_VIEWER_IS_WINDOW(self));
     priv = self->priv;
+    old_zoom = priv->zoomlevel;
 
     if (zoom_level < MIN_ZOOM_LEVEL)
         zoom_level = MIN_ZOOM_LEVEL;
@@ -1415,6 +1421,17 @@ virt_viewer_window_set_zoom_level(VirtViewerWindow *self, gint zoom_level)
     if (!priv->display)
         return;
 
+    min_zoom = virt_viewer_window_get_minimal_zoom_level(self);
+    if (min_zoom > priv->zoomlevel) {
+        g_debug("Cannot set zoom level %d, using %d", priv->zoomlevel, min_zoom);
+        priv->zoomlevel = min_zoom;
+    }
+
+    if (priv->zoomlevel == old_zoom) {
+        g_debug("Zoom level not changed, using: %d", priv->zoomlevel);
+        return;
+    }
+    
     virt_viewer_display_set_zoom_level(VIRT_VIEWER_DISPLAY(priv->display), priv->zoomlevel);
 
     virt_viewer_window_queue_resize(self);
@@ -1467,6 +1484,59 @@ virt_viewer_window_set_kiosk(VirtViewerWindow *self, gboolean enabled)
         g_debug("disabling kiosk not implemented yet");
 }
 
+static void
+virt_viewer_window_get_minimal_dimensions(VirtViewerWindow *self,
+                                          guint *width,
+                                          guint *height)
+{
+    GtkRequisition req;
+    GtkWidget *top_menu;
+
+    top_menu = GTK_WIDGET(gtk_builder_get_object(virt_viewer_window_get_builder(self), "top-menu"));
+#if !GTK_CHECK_VERSION(3, 0, 0)
+    gtk_widget_get_child_requisition(top_menu, &req);
+#else
+    gtk_widget_get_preferred_size(top_menu, &req, NULL);
+#endif
+    /* minimal dimensions of the window are the maximum of dimensions of the top-menu
+     * and minimal dimension of the display
+     */
+    *height = MAX(MIN_DISPLAY_HEIGHT, req.height);
+    *width = MAX(MIN_DISPLAY_WIDTH, req.width);
+}
+
+/**
+ * virt_viewer_window_get_minimal_zoom_level:
+ * @self: a #VirtViewerWindow
+ *
+ * Calculates the zoom level with respect to the desktop dimensions
+ *
+ * Returns: minimal possible zoom level (multiple of ZOOM_STEP)
+ */
+static gint
+virt_viewer_window_get_minimal_zoom_level(VirtViewerWindow *self)
+{
+    guint min_width, min_height;
+    guint width, height; /* desktop dimensions */
+    gint zoom;
+    double width_ratio, height_ratio;
+
+    g_return_val_if_fail(VIRT_VIEWER_IS_WINDOW(self) &&
+                         self->priv->display != NULL, MIN_ZOOM_LEVEL);
+
+    virt_viewer_window_get_minimal_dimensions(self, &min_width, &min_height);
+    virt_viewer_display_get_desktop_size(virt_viewer_window_get_display(self), &width, &height);
+
+    /* e.g. minimal width = 200, desktop width = 550 => width ratio = 0.36
+     * which means that the minimal zoom level is 40 (4 * ZOOM_STEP)
+     */
+    width_ratio = (double) min_width / width;
+    height_ratio = (double) min_height / height;
+    zoom = ceil(10 * MAX(width_ratio, height_ratio));
+
+    return MAX(MIN_ZOOM_LEVEL, zoom * ZOOM_STEP);
+}
+
 /*
  * Local variables:
  *  c-indent-level: 4
-- 
2.3.4