ply-label: Make sure get_width_of_control / get_height_of_control return correct values

Users of ply_label may want to know the height / width of the text before
calling ply_label_show, so that they can e.g. vertically align it.

This commit adds a size_needs_update bool to the label plugin and uses this
to check if executing size_control is necessary before returning the
width / height and also modifies the ply-label code to load the plugin
from its get_width / get_height methods.

As an added advantage this will also skip unnecessary size_control calls
when calling ply_label_show on an already visible label.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>

src/libply-splash-graphics/ply-label.c

@@ -299,7 +299,8 @@ long
 ply_label_get_width (ply_label_t *label)
 {
         if (label->plugin_interface == NULL)
-                return 0;
+                if (!ply_label_load_plugin (label))
+                        return 0;
 
         return label->plugin_interface->get_width_of_control (label->control);
 }
@@ -308,7 +309,8 @@ long
 ply_label_get_height (ply_label_t *label)
 {
         if (label->plugin_interface == NULL)
-                return 0;
+                if (!ply_label_load_plugin (label))
+                        return 0;
 
         return label->plugin_interface->get_height_of_control (label->control);
 }

src/plugins/controls/label/plugin.c

@@ -66,6 +66,7 @@ struct _ply_label_plugin_control
         float                alpha;
 
         uint32_t             is_hidden : 1;
+        uint32_t             needs_size_update : 1;
 };
 
 ply_label_plugin_interface_t *ply_label_plugin_get_interface (void);
@@ -93,18 +94,6 @@ destroy_control (ply_label_plugin_control_t *label)
         free (label);
 }
 
-static long
-get_width_of_control (ply_label_plugin_control_t *label)
-{
-        return label->area.width;
-}
-
-static long
-get_height_of_control (ply_label_plugin_control_t *label)
-{
-        return label->area.height;
-}
-
 static cairo_t *
 get_cairo_context_for_pixel_buffer (ply_label_plugin_control_t *label,
                                     ply_pixel_buffer_t         *pixel_buffer)
@@ -175,15 +164,20 @@ init_pango_text_layout (cairo_t       *cairo_context,
 }
 
 static void
-size_control (ply_label_plugin_control_t *label)
+size_control (ply_label_plugin_control_t *label, bool force)
 {
         cairo_t *cairo_context;
         PangoLayout *pango_layout;
         int text_width;
         int text_height;
 
-        if (label->is_hidden)
+        if (force && !label->needs_size_update)
+                return; /* Size already is up to date */
+
+        if (!force && label->is_hidden) {
+                label->needs_size_update = true;
                 return;
+        }
 
         cairo_context = get_cairo_context_for_sizing (label);
 
@@ -195,6 +189,7 @@ size_control (ply_label_plugin_control_t *label)
 
         g_object_unref (pango_layout);
         cairo_destroy (cairo_context);
+        label->needs_size_update = false;
 }
 
 static void
@@ -261,7 +256,7 @@ set_alignment_for_control (ply_label_plugin_control_t *label,
         if (label->alignment != pango_alignment) {
                 dirty_area = label->area;
                 label->alignment = pango_alignment;
-                size_control (label);
+                size_control (label, false);
                 if (!label->is_hidden && label->display != NULL)
                         ply_pixel_display_draw_area (label->display,
                                                      dirty_area.x, dirty_area.y,
@@ -278,7 +273,7 @@ set_width_for_control (ply_label_plugin_control_t *label,
         if (label->width != width) {
                 dirty_area = label->area;
                 label->width = width;
-                size_control (label);
+                size_control (label, false);
                 if (!label->is_hidden && label->display != NULL)
                         ply_pixel_display_draw_area (label->display,
                                                      dirty_area.x, dirty_area.y,
@@ -296,7 +291,7 @@ set_text_for_control (ply_label_plugin_control_t *label,
                 dirty_area = label->area;
                 free (label->text);
                 label->text = strdup (text);
-                size_control (label);
+                size_control (label, false);
                 if (!label->is_hidden && label->display != NULL)
                         ply_pixel_display_draw_area (label->display,
                                                      dirty_area.x, dirty_area.y,
@@ -317,7 +312,7 @@ set_font_for_control (ply_label_plugin_control_t *label,
                         label->fontdesc = strdup (fontdesc);
                 else
                         label->fontdesc = NULL;
-                size_control (label);
+                size_control (label, false);
                 if (!label->is_hidden && label->display != NULL)
                         ply_pixel_display_draw_area (label->display,
                                                      dirty_area.x, dirty_area.y,
@@ -358,7 +353,7 @@ show_control (ply_label_plugin_control_t *label,
 
         label->is_hidden = false;
 
-        size_control (label);
+        size_control (label, true);
 
         if (!label->is_hidden && label->display != NULL)
                 ply_pixel_display_draw_area (label->display,
@@ -389,6 +384,20 @@ is_control_hidden (ply_label_plugin_control_t *label)
         return label->is_hidden;
 }
 
+static long
+get_width_of_control (ply_label_plugin_control_t *label)
+{
+        size_control (label, true);
+        return label->area.width;
+}
+
+static long
+get_height_of_control (ply_label_plugin_control_t *label)
+{
+        size_control (label, true);
+        return label->area.height;
+}
+
 ply_label_plugin_interface_t *
 ply_label_plugin_get_interface (void)
 {