compile/run ok, issue with backlight

applications/gui/canvas.h

@@ -1,25 +1,34 @@
 #pragma once
 
 #include <stdint.h>
+#include <u8g2.h>
 
 typedef enum {
 	ColorWhite = 0x00,
 	ColorBlack = 0x01,
 } Color;
 
-typedef struct Canvas Canvas;
 typedef const uint8_t* Font;
 
-struct _CanvasApi;
-
-typedef struct _CanvasApi CanvasApi;
-
 typedef struct {
 	Font primary;
 	Font secondary;
 } Fonts;
 
-struct {
+struct _CanvasApi;
+
+typedef struct _CanvasApi CanvasApi;
+
+// Canvas is private but we need its declaration here
+typedef struct {
+    u8g2_t fb;
+    uint8_t offset_x;
+    uint8_t offset_y;
+    uint8_t width;
+    uint8_t height;
+} Canvas;
+
+struct _CanvasApi {
     Canvas canvas;
     Fonts* fonts;
     
@@ -28,8 +37,8 @@ struct {
 
     void (*clear)(CanvasApi* canvas);
 
-    void (*canvas_color_set)(CanvasApi* canvas, Color color);
-    void (*canvas_font_set)(CanvasApi* canvas, Font font);
+    void (*set_color)(CanvasApi* canvas, Color color);
+    void (*set_font)(CanvasApi* canvas, Font font);
 
     void (*draw_str)(CanvasApi* canvas, uint8_t x, uint8_t y, const char* str);
-} _CanvasApi;
+};