[almanah: 1/2] main-window: Correctly convert Pango font description to CSS

[Philip Withnall <pwithnall src gnome org>]

commit 0b944a92ebc5f5c69156a0f46b8560a35384233c
Author: Philip Withnall <withnall endlessm com>
Date:   Wed Sep 9 11:20:33 2020 +0100

    main-window: Correctly convert Pango font description to CSS
    
    A Pango font description string is not actually CSS, as it doesn’t use
    the same units. Correctly convert it using code from GTK.
    
    Solution suggested by Rinat Ibragimov.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>
    
    Fixes: #4

 src/main-window.c | 126 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 121 insertions(+), 5 deletions(-)
---
diff --git a/src/main-window.c b/src/main-window.c
index 62b0f2a..04ef71e 100644
--- a/src/main-window.c
+++ b/src/main-window.c
@@ -1404,11 +1404,125 @@ mw_setup_headerbar (AlmanahMainWindow *main_window, AlmanahApplication *applicat
        gtk_header_bar_pack_end (GTK_HEADER_BAR (main_window->priv->header_bar), button);
 }
 
+/* Taken from pango_font_description_to_css() in GTK, licensed under GPLv2+
+ * and modified to add @selector. */
+static gchar *
+font_description_to_css (PangoFontDescription *desc, const gchar *selector)
+{
+       GString *s;
+       PangoFontMask set;
+
+       s = g_string_new (selector);
+       g_string_append (s, " { ");
+
+       set = pango_font_description_get_set_fields (desc);
+       if (set & PANGO_FONT_MASK_FAMILY) {
+               g_string_append (s, "font-family: ");
+               g_string_append (s, pango_font_description_get_family (desc));
+               g_string_append (s, "; ");
+       }
+       if (set & PANGO_FONT_MASK_STYLE) {
+               switch (pango_font_description_get_style (desc)) {
+               case PANGO_STYLE_NORMAL:
+                       g_string_append (s, "font-style: normal; ");
+                       break;
+               case PANGO_STYLE_OBLIQUE:
+                       g_string_append (s, "font-style: oblique; ");
+                       break;
+               case PANGO_STYLE_ITALIC:
+                       g_string_append (s, "font-style: italic; ");
+                       break;
+               }
+       }
+       if (set & PANGO_FONT_MASK_VARIANT) {
+               switch (pango_font_description_get_variant (desc)) {
+               case PANGO_VARIANT_NORMAL:
+                       g_string_append (s, "font-variant: normal; ");
+                       break;
+               case PANGO_VARIANT_SMALL_CAPS:
+                       g_string_append (s, "font-variant: small-caps; ");
+                       break;
+               }
+       }
+       if (set & PANGO_FONT_MASK_WEIGHT) {
+               switch (pango_font_description_get_weight (desc)) {
+               case PANGO_WEIGHT_THIN:
+                       g_string_append (s, "font-weight: 100; ");
+                       break;
+               case PANGO_WEIGHT_ULTRALIGHT:
+                       g_string_append (s, "font-weight: 200; ");
+                       break;
+               case PANGO_WEIGHT_LIGHT:
+               case PANGO_WEIGHT_SEMILIGHT:
+                       g_string_append (s, "font-weight: 300; ");
+                       break;
+               case PANGO_WEIGHT_BOOK:
+               case PANGO_WEIGHT_NORMAL:
+                       g_string_append (s, "font-weight: 400; ");
+                       break;
+               case PANGO_WEIGHT_MEDIUM:
+                       g_string_append (s, "font-weight: 500; ");
+                       break;
+               case PANGO_WEIGHT_SEMIBOLD:
+                       g_string_append (s, "font-weight: 600; ");
+                       break;
+               case PANGO_WEIGHT_BOLD:
+                       g_string_append (s, "font-weight: 700; ");
+                       break;
+               case PANGO_WEIGHT_ULTRABOLD:
+                       g_string_append (s, "font-weight: 800; ");
+                       break;
+               case PANGO_WEIGHT_HEAVY:
+               case PANGO_WEIGHT_ULTRAHEAVY:
+                       g_string_append (s, "font-weight: 900; ");
+                       break;
+               }
+       }
+       if (set & PANGO_FONT_MASK_STRETCH) {
+               switch (pango_font_description_get_stretch (desc)) {
+               case PANGO_STRETCH_ULTRA_CONDENSED:
+                       g_string_append (s, "font-stretch: ultra-condensed; ");
+                       break;
+               case PANGO_STRETCH_EXTRA_CONDENSED:
+                       g_string_append (s, "font-stretch: extra-condensed; ");
+                       break;
+               case PANGO_STRETCH_CONDENSED:
+                       g_string_append (s, "font-stretch: condensed; ");
+                       break;
+               case PANGO_STRETCH_SEMI_CONDENSED:
+                       g_string_append (s, "font-stretch: semi-condensed; ");
+                       break;
+               case PANGO_STRETCH_NORMAL:
+                       g_string_append (s, "font-stretch: normal; ");
+                       break;
+               case PANGO_STRETCH_SEMI_EXPANDED:
+                       g_string_append (s, "font-stretch: semi-expanded; ");
+                       break;
+               case PANGO_STRETCH_EXPANDED:
+                       g_string_append (s, "font-stretch: expanded; ");
+                       break;
+               case PANGO_STRETCH_EXTRA_EXPANDED:
+                       g_string_append (s, "font-stretch: extra-expanded; ");
+                       break;
+               case PANGO_STRETCH_ULTRA_EXPANDED:
+                       g_string_append (s, "font-stretch: ultra-expanded; ");
+                       break;
+               }
+       }
+       if (set & PANGO_FONT_MASK_SIZE) {
+               g_string_append_printf (s, "font-size: %dpt", pango_font_description_get_size (desc) / 
PANGO_SCALE);
+       }
+
+       g_string_append (s, "}");
+
+       return g_string_free (s, FALSE);
+}
 
 static void
 mw_setup_size_text_view (AlmanahMainWindow *self)
 {
-       gchar *font_name = NULL;
+       gchar *font_desc_string = NULL;
+       PangoFontDescription *font_desc = NULL;
        gchar *css_font = NULL;
        int fixed_width;
 
@@ -1421,8 +1535,9 @@ mw_setup_size_text_view (AlmanahMainWindow *self)
                self->priv->desktop_interface_settings = g_settings_new 
(ALMANAH_MAIN_WINDOW_DESKTOP_INTERFACE_SETTINGS_SCHEMA);
                g_signal_connect (self->priv->desktop_interface_settings, "changed", G_CALLBACK 
(mw_desktop_interface_settings_changed), self);
        }
-       font_name = g_settings_get_string (self->priv->desktop_interface_settings, 
ALMANAH_MAIN_WINDOW_DOCUMENT_FONT_KEY_NAME);
-       css_font = g_strdup_printf (".almanah-mw-entry-view { font: %s; }", font_name);
+       font_desc_string = g_settings_get_string (self->priv->desktop_interface_settings, 
ALMANAH_MAIN_WINDOW_DOCUMENT_FONT_KEY_NAME);
+       font_desc = pango_font_description_from_string (font_desc_string);
+       css_font = font_description_to_css (font_desc, ".almanah-mw-entry-view");
        if (self->priv->css_provider == NULL) {
                GtkStyleContext *style_context;
 
@@ -1433,12 +1548,13 @@ mw_setup_size_text_view (AlmanahMainWindow *self)
        gtk_css_provider_load_from_data (self->priv->css_provider, css_font, strlen(css_font), NULL);
 
        /* Setting up entry GtkTextView size based on font size plus a margin */
-       fixed_width = mw_get_font_width (GTK_WIDGET (self->priv->entry_view), font_name) + 
ALMANAH_MAIN_WINDOW_FIXED_MARGIN_FONT;
+       fixed_width = mw_get_font_width (GTK_WIDGET (self->priv->entry_view), font_desc_string) + 
ALMANAH_MAIN_WINDOW_FIXED_MARGIN_FONT;
        /* The ScrolledWindow (parent container for the text view) must be at
           least the new width plus the text view margin */
        gtk_widget_set_size_request(GTK_WIDGET (self->priv->entry_view), fixed_width, -1);
 
-       g_free (font_name);
+       g_free (font_desc_string);
+       pango_font_description_free (font_desc);
        g_free (css_font);
 }