Clarify pixel address computation

1 files changed, 11 insertions, 17 deletions

diff --git a/autistdraw.c b/autistdraw.c
index f6dd2ec..258f24b 100644
--- a/autistdraw.c
+++ b/autistdraw.c
@@ -74,6 +74,8 @@ struct client
 	struct msg_reader msg_reader;       ///< Client message reader
 };
 
+#define BITMAP_PIXEL(app, x, y) (app)->bitmap[(y) * (app)->bitmap_w + (x)]
+
 typedef struct app_context app_context_t;
 struct app_context
 {
@@ -370,15 +372,10 @@ redraw_canvas (app_context_t *app)
 		int x = app->corner_x;
 		for (int screen_x = 0; screen_x < COLS; screen_x++, x++)
 		{
-			uint8_t color;
-			if (!is_in_bitmap_data (app, x, y))
-				color = 0;
-			else
-			{
-				int data_x = x - app->bitmap_x;
-				int data_y = y - app->bitmap_y;
-				color = app->bitmap[data_y * app->bitmap_w + data_x];
-			}
+			uint8_t color = 0;
+			if (is_in_bitmap_data (app, x, y))
+				color = BITMAP_PIXEL (app,
+					x - app->bitmap_x, y - app->bitmap_y);
 
 			addch (app->palette[color]);
 		}
@@ -445,10 +442,7 @@ static void
 draw_point (app_context_t *app, int x, int y, uint8_t color)
 {
 	make_place_for_point (app, x, y);
-
-	int data_x = x - app->bitmap_x;
-	int data_y = y - app->bitmap_y;
-	app->bitmap[data_y * app->bitmap_w + data_x] = color;
+	BITMAP_PIXEL (app, x - app->bitmap_x, y - app->bitmap_y) = color;
 
 	if (is_visible (app, x, y))
 	{
@@ -572,8 +566,8 @@ export_ansi (app_context_t *app)
 		const char *color = NULL;
 		for (size_t column = 0; column < w; column++)
 		{
-			const char *new_color = color_to_ansi (app->bitmap[
-				(y + row) * app->bitmap_w + (x + column)]);
+			const char *new_color = color_to_ansi
+				(BITMAP_PIXEL (app, x + column, y + row));
 			if (color != new_color)
 				fputs (new_color, fp);
 			color = new_color;
@@ -648,8 +642,8 @@ export_irc (app_context_t *app)
 		int color = MIRC_NONE;
 		for (size_t column = 0; column < w; column++)
 		{
-			int new_color = color_to_mirc (app->bitmap[
-				(y + row) * app->bitmap_w + (x + column)]);
+			int new_color = color_to_mirc
+				(BITMAP_PIXEL (app, x + column, y + row));
 			if (color != new_color)
 				fprintf (fp, "\x03%02d,%02d", new_color, new_color);
 			color = new_color;