i3 - improved tiling WM

libi3/font: Set DPI for the pango context

Patch status: merged

Patch by Bas Pape

Long description:

The pango font specification accepts a font size in points, but pango
defaults to a DPI of 96. Create a default PangoContext (which
internally creates a default PangoCairoFontMap as usual) and set the
DPI to the value of the root Screen manually.

Fixes #1115

To apply this patch, use:
curl http://cr.i3wm.org/patch/312/raw.patch | git am

b/libi3/font.c

19 
@@ -56,7 +56,10 @@ static bool load_pango_font(i3Font *font, const char *desc) {
20 
     /* Create a dummy Pango layout to compute the font height */
21 
     cairo_surface_t *surface = cairo_xcb_surface_create(conn, root_screen->root, root_visual_type, 1, 1);
22 
     cairo_t *cr = cairo_create(surface);
23 
-    PangoLayout *layout = pango_cairo_create_layout(cr);
24 
+    double ydpi = (double)root_screen->height_in_pixels * 25.4 / (double)root_screen->height_in_millimeters;
25 
+    PangoContext *pc = pango_cairo_create_context(cr);
26 
+    pango_cairo_context_set_resolution(pc, ydpi);
27 
+    PangoLayout *layout = pango_layout_new(pc);
28 
     pango_layout_set_font_description(layout, font->specific.pango_desc);
29
30 
     /* Get the font height */
31 
@@ -66,6 +69,7 @@ static bool load_pango_font(i3Font *font, const char *desc) {
32
33 
     /* Free resources */
34 
     g_object_unref(layout);
35 
+    g_object_unref(pc);
36 
     cairo_destroy(cr);
37 
     cairo_surface_destroy(surface);
38
39 
@@ -85,7 +89,10 @@ static void draw_text_pango(const char *text, size_t text_len,
40 
     cairo_surface_t *surface = cairo_xcb_surface_create(conn, drawable,
41 
             root_visual_type, x + max_width, y + savedFont->height);
42 
     cairo_t *cr = cairo_create(surface);
43 
-    PangoLayout *layout = pango_cairo_create_layout(cr);
44 
+    double ydpi = (double)root_screen->height_in_pixels * 25.4 / (double)root_screen->height_in_millimeters;
45 
+    PangoContext *pc = pango_cairo_create_context(cr);
46 
+    pango_cairo_context_set_resolution(pc, ydpi);
47 
+    PangoLayout *layout = pango_layout_new(pc);
48 
     gint height;
49
50 
     pango_layout_set_font_description(layout, savedFont->specific.pango_desc);
51 
@@ -104,6 +111,7 @@ static void draw_text_pango(const char *text, size_t text_len,
52
53 
     /* Free resources */
54 
     g_object_unref(layout);
55 
+    g_object_unref(pc);
56 
     cairo_destroy(cr);
57 
     cairo_surface_destroy(surface);
58 
 }
59 
@@ -117,7 +125,10 @@ static int predict_text_width_pango(const char *text, size_t text_len) {
60 
     /* root_visual_type is cached in load_pango_font */
61 
     cairo_surface_t *surface = cairo_xcb_surface_create(conn, root_screen->root, root_visual_type, 1, 1);
62 
     cairo_t *cr = cairo_create(surface);
63 
-    PangoLayout *layout = pango_cairo_create_layout(cr);
64 
+    double ydpi = (double)root_screen->height_in_pixels * 25.4 / (double)root_screen->height_in_millimeters;
65 
+    PangoContext *pc = pango_cairo_create_context(cr);
66 
+    pango_cairo_context_set_resolution(pc, ydpi);
67 
+    PangoLayout *layout = pango_layout_new(pc);
68
69 
     /* Get the font width */
70 
     gint width;
71 
@@ -128,6 +139,7 @@ static int predict_text_width_pango(const char *text, size_t text_len) {
72
73 
     /* Free resources */
74 
     g_object_unref(layout);
75 
+    g_object_unref(pc);
76 
     cairo_destroy(cr);
77 
     cairo_surface_destroy(surface);
78