1 files changed, 79 insertions, 0 deletions
diff --git a/platform.h b/platform.h
new file mode 100644
index 0000000..ecddb28
--- /dev/null
+++ b/platform.h
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+/*
+ * platform.h - the backend interface.
+ *
+ * The core talks only to this interface and never includes an OS header.
+ * Exactly one backend is linked into the binary, so there is a single
+ * platform_init() symbol and main.c needs no #ifdef.
+ *
+ * All coordinates are global, logical pixels: the union of every screen laid
+ * out in the display server's coordinate space.
+ */
+#ifndef MOUSEBOARD_PLATFORM_H
+#define MOUSEBOARD_PLATFORM_H
+
+#include <stdint.h>
+
+#define MB_MAX_SCREENS 16
+
+/* One monitor, positioned in the global coordinate space. */
+struct mb_screen {
+	int x, y, w, h;
+};
+
+/* A drawable overlay surface for one screen, ARGB8888, native byte order
+ * (0xAARRGGBB). w,h are LOGICAL pixels - the core draws in these and stays
+ * scale-agnostic. The backing store is w*scale by h*scale device pixels;
+ * stride is device pixels per row. The renderer multiplies by scale. */
+struct mb_buffer {
+	uint32_t *px;
+	int w, h;	/* logical size */
+	int stride;	/* device pixels per row */
+	int scale;	/* integer output scale (1 = non-HiDPI) */
+};
+
+enum mb_button { MB_LEFT = 0, MB_MIDDLE = 1, MB_RIGHT = 2 };
+
+/* Keys handed to the core. Printable input arrives as its ASCII code
+ * (0x20..0x7e); nothing else reaches the core except these. */
+enum {
+	MB_KEY_NONE = 0,	  /* overlay closed / connection lost */
+	MB_KEY_ESC = 0x01000000,
+	MB_KEY_BACKSPACE,
+	MB_KEY_ENTER,
+};
+
+struct platform {
+	int n_screens;
+	struct mb_screen screens[MB_MAX_SCREENS];
+
+	/* Return screen i's overlay buffer, cleared to fully transparent. */
+	struct mb_buffer *(*frame_begin)(struct platform *, int screen);
+	/* Present every buffer drawn since the last commit. */
+	int (*frame_commit)(struct platform *);
+	/* Block until the next key; returns an ASCII code or MB_KEY_*. */
+	uint32_t (*next_key)(struct platform *);
+	/* Warp the pointer to a global position. */
+	int (*pointer_move)(struct platform *, int x, int y);
+	/* Press (press=1) or release (press=0) a button. */
+	int (*pointer_button)(struct platform *, enum mb_button, int press);
+	/* Tear down the overlay and disconnect. */
+	void (*teardown)(struct platform *);
+
+	void *priv;
+};
+
+/* Run once at process start, before any argument parsing or output: the
+ * Windows backend attaches to a parent console there so --help and --dry-run
+ * still print from a terminal. A no-op elsewhere. */
+void platform_early_init(void);
+
+/* Bring up the backend: connect to the display server, create the fullscreen
+ * overlay surfaces, and grab the keyboard. Returns NULL on failure (prints why
+ * to stderr). */
+struct platform *platform_init(void);
+
+/* Sleep for ms milliseconds; used only to space out synthesized button
+ * presses. Provided by the backend so the core needs no OS header. */
+void platform_sleep_ms(int ms);
+
+#endif /* MOUSEBOARD_PLATFORM_H */