feat(draw): add initial SDL renderer

It caches SW rendered bitmaps in textures.
The cache is also updated to support data and source separately.
E.g. source is a path to an image, and if that image changes all
related cache entries needs to found and invalidated.

Limitations of SDL rederer:
- not all draw task types are supported
- image transformation is not supported
- some textures (e.g. button matrix texts) are not detected as cached
- images are not cached
- images are supported only from path

src/draw/sdl/lv_draw_sdl.h

@@ -0,0 +1,89 @@
+/**
+ * @file lv_draw_sw.h
+ *
+ */
+
+#ifndef LV_DRAW_SW_H
+#define LV_DRAW_SW_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*********************
+ *      INCLUDES
+ *********************/
+#include "../lv_draw.h"
+#if LV_USE_DRAW_SDL
+
+#include "../../misc/lv_area.h"
+#include "../../misc/lv_color.h"
+#include "../../display/lv_display.h"
+#include "../../osal/lv_os.h"
+
+/*********************
+ *      DEFINES
+ *********************/
+
+/**********************
+ *      TYPEDEFS
+ **********************/
+
+typedef struct {
+    lv_draw_unit_t base_unit;
+    struct _lv_draw_task_t * task_act;
+    uint32_t texture_cache_data_type;
+} lv_draw_sdl_unit_t;
+
+#if LV_DRAW_SW_SHADOW_CACHE_SIZE
+typedef struct {
+    uint8_t cache[LV_DRAW_SW_SHADOW_CACHE_SIZE * LV_DRAW_SW_SHADOW_CACHE_SIZE];
+    int32_t cache_size;
+    int32_t cache_r;
+} lv_draw_sw_shadow_cache_t;
+#endif
+
+/**********************
+ * GLOBAL PROTOTYPES
+ **********************/
+
+void lv_draw_sdl_init(void);
+
+LV_ATTRIBUTE_FAST_MEM void lv_draw_sdl_image(lv_draw_unit_t * draw_unit, const lv_draw_image_dsc_t * draw_dsc,
+                                             const lv_area_t * coords);
+
+void lv_draw_sdl_fill(lv_draw_unit_t * draw_unit, const lv_draw_fill_dsc_t * dsc, const lv_area_t * coords);
+
+void lv_draw_sdl_border(lv_draw_unit_t * draw_unit, const lv_draw_border_dsc_t * dsc, const lv_area_t * coords);
+
+void lv_draw_sdl_box_shadow(lv_draw_unit_t * draw_unit, const lv_draw_box_shadow_dsc_t * dsc, const lv_area_t * coords);
+
+void lv_draw_sdl_bg_image(lv_draw_unit_t * draw_unit, const lv_draw_bg_image_dsc_t * dsc, const lv_area_t * coords);
+
+void lv_draw_sdl_label(lv_draw_unit_t * draw_unit, const lv_draw_label_dsc_t * dsc, const lv_area_t * coords);
+
+void lv_draw_sdl_arc(lv_draw_unit_t * draw_unit, const lv_draw_arc_dsc_t * dsc, const lv_area_t * coords);
+
+LV_ATTRIBUTE_FAST_MEM void lv_draw_sdl_line(lv_draw_unit_t * draw_unit, const lv_draw_line_dsc_t * dsc);
+
+void lv_draw_sdl_layer(lv_draw_unit_t * draw_unit, const lv_draw_image_dsc_t * draw_dsc, const lv_area_t * coords);
+
+void lv_draw_sdl_triangle(lv_draw_unit_t * draw_unit, const lv_draw_triangle_dsc_t * dsc);
+
+void lv_draw_sdl_mask_rect(lv_draw_unit_t * draw_unit, const lv_draw_mask_rect_dsc_t * dsc, const lv_area_t * coords);
+
+/***********************
+ * GLOBAL VARIABLES
+ ***********************/
+
+/**********************
+ *      MACROS
+ **********************/
+
+#endif /*LV_USE_DRAW_SDL*/
+
+#ifdef __cplusplus
+} /*extern "C"*/
+#endif
+
+#endif /*LV_DRAW_SDL_H*/