Add standalone render context module

include/display/render/context.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define RGB565(R, G, B) \
+    ((uint16_t)((((uint16_t)(R) & 0xF8u) << 8) | \
+                (((uint16_t)(G) & 0xFCu) << 3) | \
+                (((uint16_t)(B) & 0xF8u) >> 3)))
+
+#define BSWAP16(X) \
+    ((uint16_t)((((uint16_t)(X) & 0x00FFu) << 8) | \
+                (((uint16_t)(X) & 0xFF00u) >> 8)))
+
+/* RGB888 -> RGB565 with swapped byte order for ctx->buf */
+#define RGB16(R, G, B) BSWAP16(RGB565((R), (G), (B)))
+
+typedef struct
+{
+    uint16_t* buf;
+    uint16_t width;
+    uint16_t height;
+    uint16_t clip_x0;
+    uint16_t clip_y0;
+    uint16_t clip_x1;
+    uint16_t clip_y1;
+} render_ctx_t;
+
+void render_begin(render_ctx_t* ctx, uint16_t* buf, uint16_t width, uint16_t height);
+void render_set_clip(render_ctx_t* ctx, uint16_t x, uint16_t y, uint16_t width, uint16_t height);
+void render_reset_clip(render_ctx_t* ctx);
+void render_clear(render_ctx_t* ctx, uint16_t color);
+void render_pixel(render_ctx_t* ctx, int x, int y, uint16_t color);
+
+#ifdef __cplusplus
+}
+#endif