2 files changed, 7 insertions, 0 deletions

diff --git a/plat.c b/plat.c
index 5fbfb19..da32e29 100644
--- a/plat.c
+++ b/plat.c
@@ -266,6 +266,7 @@ typedef struct {
 	GC gc;
 	int w, h;
 	int rmx, rmy;
+	int omx, omy;
 	int ms;
 	unsigned long begin, end;
 	XImage* bb;
@@ -382,6 +383,7 @@ App* new_app(Heap* mem, int w, int h, const char* n) {
 	a->w = w;
 	a->h = h;
 	i->d = XOpenDisplay(0);
+	i->omx = i->omy = 0;
 	if (!i->d) {
 		print_err("Failed to open X11 display.\n");
 		pbreak(error_platform_error);
@@ -459,6 +461,10 @@ void app_begin(App* a) {
 				break;
 		}
 	}
+	a->dmx = a->mx - i->omx;
+	a->dmy = a->my - i->omy;
+	i->omx = a->mx;
+	i->omy = a->my;
 }
 
 void app_rencpy(
diff --git a/plat.h b/plat.h
index a4e2758..1d79465 100644
--- a/plat.h
+++ b/plat.h
@@ -68,6 +68,7 @@ typedef struct {
 	int w, h, s, o, mpf;
 	int fps;
 	int mx, my;
+	int dmx, dmy;
 	Error err;
 	Colour* fb;
 	Heap* heap;