Add "Scale (fit)" background image mode

The current "Scale" mode crops out part of the image if the scaled
image is larger than the terminal in any direction. This is useful for
most cases, such as wallpapers repurposed as terminal backgrounds.
However, this may be surprising to users coming from xfce4-terminal,
where the equivalent "Scaled" mode tries to fit the background within
the terminal in both dimensions. This new "Scale (fit)" mode is meant
to emulate this behaviour.

data/gsettings/com.gexperts.Tilix.gschema.xml

@@ -37,9 +37,10 @@
   <!-- Background Image Options -->
   <enum id='com.gexperts.Tilix.Background.Image.Mode'>
     <value nick='scale' value='0'/>
-    <value nick='tile' value='1'/>
-    <value nick='center' value='2'/>
-    <value nick='stretch' value='3'/>
+    <value nick='scale-fit' value='1'/>
+    <value nick='tile' value='2'/>
+    <value nick='center' value='3'/>
+    <value nick='stretch' value='4'/>
   </enum>
 
   <!-- Background Image Scaling Options, note these

source/gx/gtk/cairo.d

@@ -111,7 +111,7 @@ Pixbuf getWidgetImage(Widget widget, double factor, int width, int height) {
     }
 }
 
-enum ImageLayoutMode {SCALE, TILE, CENTER, STRETCH};
+enum ImageLayoutMode {SCALE, SCALE_FIT, TILE, CENTER, STRETCH};
 
 ImageSurface renderImage(Pixbuf pb, bool alpha = false) {
     cairo_format_t format = alpha?cairo_format_t.ARGB32:cairo_format_t.RGB24;
@@ -172,6 +172,23 @@ void renderImage(Context cr, ImageSurface isSource, int outputWidth, int outputH
             cr.getSource().setFilter(scaleMode);
             cr.paint();
             break;
+        case ImageLayoutMode.SCALE_FIT:
+            // Emulate xfce4-terminal's "Scaled" behaviour -- scale the image
+            // such that it fills the dimension with the shortest length and
+            // fits both the x and y dimensions.
+            double xScale = to!double(outputWidth) / to!double(isSource.getWidth());
+            double yScale = to!double(outputHeight) / to!double(isSource.getHeight());
+            double scale = min(xScale, yScale);
+
+            double xOffset = (outputWidth - (isSource.getWidth() * scale)) / 2.0;
+            double yOffset = (outputHeight - (isSource.getHeight() * scale)) / 2.0;
+
+            cr.translate(xOffset, yOffset);
+            cr.scale(scale, scale);
+            cr.setSourceSurface(isSource, 0, 0);
+            cr.getSource().setFilter(scaleMode);
+            cr.paint();
+            break;
         case ImageLayoutMode.TILE:
             cr.setSourceSurface(isSource, 0, 0);
             cr.getSource().setExtend(cairo_extend_t.REPEAT);

source/gx/tilix/appwindow.d

@@ -2034,6 +2034,9 @@ public:
             case SETTINGS_BACKGROUND_IMAGE_MODE_SCALE_VALUE:
                 mode = ImageLayoutMode.SCALE;
                 break;
+            case SETTINGS_BACKGROUND_IMAGE_MODE_SCALE_FIT_VALUE:
+                mode = ImageLayoutMode.SCALE_FIT;
+                break;
             case SETTINGS_BACKGROUND_IMAGE_MODE_TILE_VALUE:
                 mode = ImageLayoutMode.TILE;
                 break;

source/gx/tilix/prefeditor/prefdialog.d

@@ -1199,7 +1199,7 @@ class AppearancePreferences: Box {
                 gsSettings.reset(SETTINGS_BACKGROUND_IMAGE_KEY);
             });
 
-            ComboBox cbImageMode = createNameValueCombo([_("Scale"), _("Tile"), _("Center"),_("Stretch")], SETTINGS_BACKGROUND_IMAGE_MODE_VALUES);
+            ComboBox cbImageMode = createNameValueCombo([_("Scale"), _("Scale (fit)"), _("Tile"), _("Center"),_("Stretch")], SETTINGS_BACKGROUND_IMAGE_MODE_VALUES);
             bh.bind(SETTINGS_BACKGROUND_IMAGE_MODE_KEY, cbImageMode, "active-id", GSettingsBindFlags.DEFAULT);
 
             // Background image settings only enabled if transparency is enabled

source/gx/tilix/preferences.d

@@ -105,10 +105,11 @@ enum SETTINGS_BACKGROUND_IMAGE_KEY = "background-image";
 enum SETTINGS_BACKGROUND_IMAGE_SCALE_KEY = "background-image-scale";
 enum SETTINGS_BACKGROUND_IMAGE_MODE_KEY = "background-image-mode";
 enum SETTINGS_BACKGROUND_IMAGE_MODE_SCALE_VALUE = "scale";
+enum SETTINGS_BACKGROUND_IMAGE_MODE_SCALE_FIT_VALUE = "scale-fit";
 enum SETTINGS_BACKGROUND_IMAGE_MODE_TILE_VALUE = "tile";
 enum SETTINGS_BACKGROUND_IMAGE_MODE_CENTER_VALUE = "center";
 enum SETTINGS_BACKGROUND_IMAGE_MODE_STRETCH_VALUE = "stretch";
-immutable string[] SETTINGS_BACKGROUND_IMAGE_MODE_VALUES = [SETTINGS_BACKGROUND_IMAGE_MODE_SCALE_VALUE,SETTINGS_BACKGROUND_IMAGE_MODE_TILE_VALUE,SETTINGS_BACKGROUND_IMAGE_MODE_CENTER_VALUE,SETTINGS_BACKGROUND_IMAGE_MODE_STRETCH_VALUE];
+immutable string[] SETTINGS_BACKGROUND_IMAGE_MODE_VALUES = [SETTINGS_BACKGROUND_IMAGE_MODE_SCALE_VALUE,SETTINGS_BACKGROUND_IMAGE_MODE_SCALE_FIT_VALUE,SETTINGS_BACKGROUND_IMAGE_MODE_TILE_VALUE,SETTINGS_BACKGROUND_IMAGE_MODE_CENTER_VALUE,SETTINGS_BACKGROUND_IMAGE_MODE_STRETCH_VALUE];
 
 enum SETTINGS_SIDEBAR_RIGHT = "sidebar-on-right";
 enum SETTINGS_RECENT_SESSION_FILES_KEY = "recent-session-files";