Set dark background for help text block

Makes help text more readable on white images.

Resolves #185.

Signed-off-by: Artem Senichev <artemsen@gmail.com>

src/application.c

@@ -426,8 +426,8 @@ bool app_init(struct config* cfg, const char** sources, size_t num)
 
     // initialize other subsystems
     font_init(cfg);
-    info_init(cfg);
     keybind_init(cfg);
+    info_init(cfg);
     loader_init();
     viewer_init(cfg, ctx.ehandler == viewer_handle ? first_image : NULL);
     gallery_init(cfg, ctx.ehandler == gallery_handle ? first_image : NULL);
@@ -455,8 +455,8 @@ void app_destroy(void)
     viewer_destroy();
     ui_destroy();
     image_list_destroy();
-    keybind_destroy();
     info_destroy();
+    keybind_destroy();
     font_destroy();
 
     for (size_t i = 0; i < ctx.wfds_num; ++i) {

src/info.c

@@ -236,6 +236,11 @@ static void print_help(struct pixmap* window)
         top = window->height / 2 - (rows * line_height) / 2;
     }
 
+    // darken text block background
+    pixmap_blend(window, left - TEXT_PADDING, top - TEXT_PADDING,
+                 total_width + TEXT_PADDING, rows * line_height + TEXT_PADDING,
+                 ARGB(0xa0, 0, 0, 0));
+
     // put text on window
     for (size_t col = 0; col < columns; ++col) {
         size_t y = top;

src/pixmap.c

@@ -94,6 +94,22 @@ void pixmap_inverse_fill(struct pixmap* pm, ssize_t x, ssize_t y, size_t width,
     }
 }
 
+void pixmap_blend(struct pixmap* pm, ssize_t x, ssize_t y, size_t width,
+                  size_t height, argb_t color)
+{
+    const ssize_t left = max(0, x);
+    const ssize_t top = max(0, y);
+    const ssize_t right = min((ssize_t)pm->width, x + (ssize_t)width);
+    const ssize_t bottom = min((ssize_t)pm->height, y + (ssize_t)height);
+
+    for (y = top; y < bottom; ++y) {
+        argb_t* line = &pm->data[y * pm->width];
+        for (x = left; x < right; ++x) {
+            alpha_blend(color, &line[x]);
+        }
+    }
+}
+
 void pixmap_hline(struct pixmap* pm, ssize_t x, ssize_t y, size_t width,
                   argb_t color)
 {
@@ -163,22 +179,22 @@ void pixmap_grid(struct pixmap* pm, ssize_t x, ssize_t y, size_t width,
     }
 }
 
-void pixmap_apply_mask(struct pixmap* dst, ssize_t x, ssize_t y,
+void pixmap_apply_mask(struct pixmap* pm, ssize_t x, ssize_t y,
                        const uint8_t* mask, size_t width, size_t height,
                        argb_t color)
 {
     const ssize_t left = max(0, x);
     const ssize_t top = max(0, y);
-    const ssize_t right = min((ssize_t)dst->width, x + (ssize_t)width);
-    const ssize_t bottom = min((ssize_t)dst->height, y + (ssize_t)height);
+    const ssize_t right = min((ssize_t)pm->width, x + (ssize_t)width);
+    const ssize_t bottom = min((ssize_t)pm->height, y + (ssize_t)height);
     const ssize_t dst_width = right - left;
     const ssize_t delta_x = left - x;
     const ssize_t delta_y = top - y;
 
     for (ssize_t dst_y = top; dst_y < bottom; ++dst_y) {
         const size_t src_y = dst_y - top + delta_y;
         const uint8_t* mask_line = &mask[src_y * width + delta_x];
-        argb_t* dst_line = &dst->data[dst_y * dst->width + left];
+        argb_t* dst_line = &pm->data[dst_y * pm->width + left];
 
         for (x = 0; x < dst_width; ++x) {
             const uint8_t alpha_mask = mask_line[x];

src/pixmap.h

@@ -80,6 +80,16 @@ void pixmap_fill(struct pixmap* pm, ssize_t x, ssize_t y, size_t width,
 void pixmap_inverse_fill(struct pixmap* pm, ssize_t x, ssize_t y, size_t width,
                          size_t height, argb_t color);
 
+/**
+ * Blend area with specified color.
+ * @param pm pixmap context
+ * @param x,y start coordinates, left top point
+ * @param width,height region size
+ * @param color color to set
+ */
+void pixmap_blend(struct pixmap* pm, ssize_t x, ssize_t y, size_t width,
+                  size_t height, argb_t color);
+
 /**
  * Draw horizontal line.
  * @param pm pixmap context
@@ -124,13 +134,13 @@ void pixmap_grid(struct pixmap* pm, ssize_t x, ssize_t y, size_t width,
 
 /**
  * Apply mask to pixmap: change color according alpha channel.
- * @param dst destination pixmap
+ * @param pm destination pixmap
  * @param x,y destination left top point
  * @param mask array with alpha channel mask
  * @param width,height mask size
  * @param color color to set
  */
-void pixmap_apply_mask(struct pixmap* dst, ssize_t x, ssize_t y,
+void pixmap_apply_mask(struct pixmap* pm, ssize_t x, ssize_t y,
                        const uint8_t* mask, size_t width, size_t height,
                        argb_t color);