From 2932570460af0b47584cea2bde537476147d1f36 Mon Sep 17 00:00:00 2001
From: Fabian Vogt <fvogt@suse.com>
Date: Fri, 20 Jan 2017 14:02:30 +0100
Subject: [PATCH v3 4/4] Add HiDPI support to label-ft plugin

FreeType allows us to specify horizontal and vertical resolutions,
so do just that.
As we only know the scale factor in the drawing function, the current
setting is saved to avoid unnecessary calls to FT_Set_Char_Size.
---
 src/plugins/controls/label-ft/plugin.c | 51 ++++++++++++++++++++++++++++------
 1 file changed, 42 insertions(+), 9 deletions(-)

diff --git a/src/plugins/controls/label-ft/plugin.c b/src/plugins/controls/label-ft/plugin.c
index 7872d8b..6d186e2 100644
--- a/src/plugins/controls/label-ft/plugin.c
+++ b/src/plugins/controls/label-ft/plugin.c
@@ -56,6 +56,11 @@ struct _ply_label_plugin_control
         FT_Library             library;
         FT_Face                face;
 
+        unsigned long          size;
+        /* If size is not in px, scaling for HiDPI is applied. */
+        bool                   size_in_px;
+        uint32_t               cur_scale;
+
         char                  *text;
         float                  red;
         float                  green;
@@ -85,6 +90,32 @@ query_fc_match ()
         return fc_match_out;
 }
 
+/* If size_in_px is false, this adjusts for DPI. */
+static bool
+set_font_size (ply_label_plugin_control_t *label,
+               unsigned long size,
+               bool size_in_px,
+               uint32_t scale)
+{
+        if (label->size == size && label->size_in_px == size_in_px && label->cur_scale == scale)
+                return true;
+
+        if (label->size_in_px) {
+                if (FT_Set_Pixel_Sizes (label->face, 0, size) != 0)
+                        return false;
+        }
+        else {
+                if (FT_Set_Char_Size (label->face, FT_PX_TO_GRID(size), 0, 100 * scale, 0) != 0)
+                        return false;
+        }
+
+        label->size = size;
+        label->size_in_px = size_in_px;
+        label->cur_scale = scale;
+
+        return true;
+}
+
 static ply_label_plugin_control_t *
 create_control (void)
 {
@@ -122,9 +153,8 @@ create_control (void)
                 }
         }
 
-        /* 12pt/100dpi as default */
-        error = FT_Set_Char_Size (label->face, FT_PX_TO_GRID(12), 0, 100, 0);
-        if (error) {
+        /* 12pt as default */
+        if (!set_font_size (label, 12, false, 1)) {
                 FT_Done_Face (label->face);
                 FT_Done_FreeType (label->library);
                 free (label);
@@ -279,6 +309,7 @@ draw_control (ply_label_plugin_control_t *label,
         const char     *cur_c;
         uint32_t       *target;
         ply_rectangle_t target_size;
+        uint32_t        scale;
 
         if (label->is_hidden)
                 return;
@@ -290,6 +321,12 @@ draw_control (ply_label_plugin_control_t *label,
             || label->area.y + (long) label->area.height < y)
             return;
 
+        /* The display scale could have changed. */
+        scale = ply_pixel_buffer_get_device_scale (pixel_buffer);
+
+        /* This could fail, but it's better to draw with wrong scaling than not at all. */
+        set_font_size (label, label->size, label->size_in_px, scale);
+
         slot = label->face->glyph;
 
         cur_c = label->text;
@@ -394,12 +431,8 @@ set_font_for_control (ply_label_plugin_control_t *label,
                 size_in_pixels = true;
         }
 
-        if (size_in_pixels)
-                FT_Set_Pixel_Sizes (label->face, 0, size);
-        else
-                FT_Set_Char_Size (label->face, FT_PX_TO_GRID(size), 0, 100, 0);
-
-        /* Ignore errors, to keep the current size. */
+        /* If this fails, the current size is kept */
+        set_font_size (label, size, size_in_pixels, label->cur_scale);
 
         trigger_redraw (label, true);
 }
-- 
2.11.0