From 28e7cd30065719c5418b9c7263e8acd34bd739d5 Mon Sep 17 00:00:00 2001
From: Jens Peters <jp7677@gmail.com>
Date: Mon, 1 Jan 2024 18:26:44 +0100
Subject: [PATCH] input: add area transformation for tablet coordinates

---
 src/input/tablet.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/input/tablet.c b/src/input/tablet.c
index 3ea70c4b..662ce0c7 100644
--- a/src/input/tablet.c
+++ b/src/input/tablet.c
@@ -11,6 +11,34 @@
 #include "input/cursor.h"
 #include "input/tablet.h"
 
+static void
+adjust_for_tablet_area(double tablet_width, double tablet_height,
+		struct wlr_fbox box, double *x, double *y)
+{
+	if ((!box.x && !box.y && !box.width && !box.height)
+			|| !tablet_width || !tablet_height) {
+		return;
+	}
+
+	if (!box.width) {
+		box.width = tablet_width - box.x;
+	}
+	if (!box.height) {
+		box.height = tablet_height - box.y;
+	}
+
+	if (box.x + box.width <= tablet_width) {
+		const double max_x = 1;
+		double width_offset = max_x * box.x / tablet_width;
+		*x = (*x - width_offset) * tablet_width / box.width;
+	}
+	if (box.y + box.height <= tablet_height) {
+		const double max_y = 1;
+		double height_offset = max_y * box.y / tablet_height;
+		*y = (*y - height_offset) * tablet_height / box.height;
+	}
+}
+
 static void
 adjust_for_rotation(enum rotation rotation, double *x, double *y)
 {
@@ -50,6 +78,8 @@ handle_axis(struct wl_listener *listener, void *data)
 
 		double x = tablet->x;
 		double y = tablet->y;
+		adjust_for_tablet_area(tablet->tablet->width_mm, tablet->tablet->height_mm,
+			rc.tablet.box, &x, &y);
 		adjust_for_rotation(rc.tablet.rotation, &x, &y);
 		cursor_emulate_move_absolute(tablet->seat, &ev->tablet->base, x, y, ev->time_msec);
 	}