Merge branch 'scale-fonts-using-logical-dpi-plus-scale-factor'

CHANGELOG.md

@@ -18,6 +18,8 @@
 * Window size doubling when moving window between outputs with
   different scaling factors (https://codeberg.org/dnkl/foot/issues/3).
 * Sixel images moved or deleted on window resize.
+* Font being too small on monitors with fractional scaling
+  (https://codeberg.org/dnkl/foot/issues/5).
 
 ### Security
 

terminal.c

@@ -532,18 +532,39 @@ term_set_fonts(struct terminal *term, struct font *fonts[static 4])
 static unsigned
 get_font_dpi(const struct terminal *term)
 {
+    /*
+     * Use output's DPI to scale font. This is to ensure the font has
+     * the same physical height (if measured by a ruler) regardless of
+     * monitor.
+     *
+     * Conceptually, we use the physical monitor specs to calculate
+     * the DPI, and we ignore the output's scaling factor.
+     *
+     * However, to deal with fractional scaling, where we're told to
+     * render at e.g. 2x, but are then downscaled by the compositor to
+     * e.g. 1.25, we use the scaled DPI value multiplied by the scale
+     * factor instead.
+     *
+     * For integral scaling factors the resulting DPI is the same as
+     * if we had used the physical DPI.
+     *
+     * For fractional scaling factors we'll get a DPI *larger* than
+     * the physical DPI, that ends up being right when later
+     * downscaled by the compositor.
+     */
+
     /* Use highest DPI from outputs we're mapped on */
     unsigned dpi = 0;
     assert(term->window != NULL);
     tll_foreach(term->window->on_outputs, it) {
-        if (it->item->y_ppi > dpi)
-            dpi = it->item->y_ppi;
+        if (it->item->ppi.scaled.y > dpi)
+            dpi = it->item->ppi.scaled.y * term->scale;
     }
 
     /* If we're not mapped, use DPI from first monitor. Hopefully this is where we'll get mapped later... */
     if (dpi == 0) {
         tll_foreach(term->wl->monitors, it) {
-            dpi = it->item.y_ppi;
+            dpi = it->item.ppi.scaled.y * term->scale;
             break;
         }
     }

wayland.c

@@ -169,10 +169,16 @@ update_terms_on_monitor(struct monitor *mon)
 static void
 output_update_ppi(struct monitor *mon)
 {
-    int x_inches = mon->width_mm * 0.03937008;
-    int y_inches = mon->height_mm * 0.03937008;
-    mon->x_ppi = mon->width_px / x_inches;
-    mon->y_ppi = mon->height_px / y_inches;
+    if (mon->dim.mm.width == 0 || mon->dim.mm.height == 0)
+        return;
+
+    int x_inches = mon->dim.mm.width * 0.03937008;
+    int y_inches = mon->dim.mm.height * 0.03937008;
+    mon->ppi.real.x = mon->dim.px_real.width / x_inches;
+    mon->ppi.real.y = mon->dim.px_real.height / y_inches;
+
+    mon->ppi.scaled.x = mon->dim.px_scaled.width / x_inches;
+    mon->ppi.scaled.y = mon->dim.px_scaled.height / y_inches;
 }
 
 static void
@@ -182,9 +188,9 @@ output_geometry(void *data, struct wl_output *wl_output, int32_t x, int32_t y,
                 int32_t transform)
 {
     struct monitor *mon = data;
-    mon->width_mm = physical_width;
-    mon->height_mm = physical_height;
-    mon->inch = sqrt(pow(mon->width_mm, 2) + pow(mon->height_mm, 2)) * 0.03937008;
+    mon->dim.mm.width = physical_width;
+    mon->dim.mm.height = physical_height;
+    mon->inch = sqrt(pow(mon->dim.mm.width, 2) + pow(mon->dim.mm.height, 2)) * 0.03937008;
     mon->make = make != NULL ? strdup(make) : NULL;
     mon->model = model != NULL ? strdup(model) : NULL;
     output_update_ppi(mon);
@@ -199,8 +205,8 @@ output_mode(void *data, struct wl_output *wl_output, uint32_t flags,
 
     struct monitor *mon = data;
     mon->refresh = (float)refresh / 1000;
-    mon->width_px = width;
-    mon->height_px = height;
+    mon->dim.px_real.width = width;
+    mon->dim.px_real.height = height;
     output_update_ppi(mon);
 }
 
@@ -238,6 +244,10 @@ static void
 xdg_output_handle_logical_size(void *data, struct zxdg_output_v1 *xdg_output,
                                int32_t width, int32_t height)
 {
+    struct monitor *mon = data;
+    mon->dim.px_scaled.width = width;
+    mon->dim.px_scaled.height = height;
+    output_update_ppi(mon);
 }
 
 static void
@@ -786,11 +796,12 @@ wayl_init(const struct config *conf, struct fdm *fdm)
 
     tll_foreach(wayl->monitors, it) {
         LOG_INFO(
-            "%s: %dx%d+%dx%d@%dHz %s (%.2f\", PPI=%dx%d, scale=%d)",
-            it->item.name, it->item.width_px, it->item.height_px,
-            it->item.x, it->item.y, (int)round(it->item.refresh), it->item.model, it->item.inch,
-            it->item.x_ppi, it->item.y_ppi,
-            it->item.scale);
+            "%s: %dx%d+%dx%d@%dHz %s %.2f\" scale=%d PPI=%dx%d (physical) PPI=%dx%d (logical)",
+            it->item.name, it->item.dim.px_real.width, it->item.dim.px_real.height,
+            it->item.x, it->item.y, (int)round(it->item.refresh),
+            it->item.model, it->item.inch, it->item.scale,
+            it->item.ppi.real.x, it->item.ppi.real.y,
+            it->item.ppi.scaled.x, it->item.ppi.scaled.y);
     }
 
     /* Clipboard */

wayland.h

@@ -24,14 +24,39 @@ struct monitor {
     int x;
     int y;
 
-    int width_mm;
-    int height_mm;
+    struct {
+        /* Physical size, in mm */
+        struct {
+            int width;
+            int height;
+        } mm;
 
-    int width_px;
-    int height_px;
+        /* Physical size, in pixels */
+        struct {
+            int width;
+            int height;
+        } px_real;
 
-    int x_ppi;
-    int y_ppi;
+        /* Scaled size, in pixels */
+        struct {
+            int width;
+            int height;
+        } px_scaled;
+    } dim;
+
+    struct {
+        /* PPI, based on physical size */
+        struct {
+            int x;
+            int y;
+        } real;
+
+        /* PPI, logical, based on scaled size */
+        struct {
+            int x;
+            int y;
+        } scaled;
+    } ppi;
 
     int scale;
     float refresh;