fb: cfb: add API to set font kerning

Font kerning was used but it was not possible to change it.
Also, font_idx was set to zero twice in init.

Signed-off-by: Simon Frank <[email protected]>

Author: Simon Frank

include/zephyr/display/cfb.h

@@ -153,6 +153,16 @@ int cfb_get_display_parameter(const struct device *dev,
  */
 int cfb_framebuffer_set_font(const struct device *dev, uint8_t idx);
 
+/**
+ * @brief Set font kerning (spacing between individual letters).
+ *
+ * @param dev Pointer to device structure for driver instance
+ * @param kerning Font kerning
+ *
+ * @return 0 on success, negative value otherwise
+ */
+int cfb_set_kerning(const struct device *dev, int8_t kerning);
+
 /**
  * @brief Get font size.
  *

subsys/fb/cfb.c

@@ -316,6 +316,13 @@ int cfb_get_font_size(const struct device *dev, uint8_t idx, uint8_t *width,
 	return 0;
 }
 
+int cfb_set_kerning(const struct device *dev, int8_t kerning)
+{
+	char_fb.kerning = kerning;
+
+	return 0;
+}
+
 int cfb_get_numof_fonts(const struct device *dev)
 {
 	const struct char_framebuffer *fb = &char_fb;
@@ -343,7 +350,6 @@ int cfb_framebuffer_init(const struct device *dev)
 	fb->pixel_format = cfg.current_pixel_format;
 	fb->screen_info = cfg.screen_info;
 	fb->buf = NULL;
-	fb->font_idx = 0U;
 	fb->kerning = 0;
 	fb->inverted = false;