From 9cc66495cfb6393102ce5ad4e82f2ccb716b9b33 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=A9my=20Zurcher?= <jeremy@asynk.ch>
Date: Sat, 2 Nov 2019 11:17:22 +0100
Subject: [PATCH] Android : implement InputEventMagnifyGesture and
 InputEventPanGesture

sets threshold constants PAN_GESTURE_MIN_DELTA and MAGNIFY_GESTURE_MIN_FACTOR
---
 platform/android/os_android.cpp | 34 ++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/platform/android/os_android.cpp b/platform/android/os_android.cpp
index defee8f1f17..9156181bbee 100644
--- a/platform/android/os_android.cpp
+++ b/platform/android/os_android.cpp
@@ -49,6 +49,9 @@
 #include "java_godot_io_wrapper.h"
 #include "java_godot_wrapper.h"
 
+#define PAN_GESTURE_MIN_DELTA 5 // only advertise PanGesture event with dx and dy greater than this
+#define MAGNIFY_GESTURE_MIN_FACTOR 0.1 // only advertise MagnifyGesture event with a factor difference from 1.0 greater than this
+
 class AndroidLogger : public Logger {
 public:
 	virtual void logv(const char *p_format, va_list p_list, bool p_err) {
@@ -406,6 +409,35 @@ void OS_Android::process_touch(int p_what, int p_pointer, const Vector<TouchPos>
 
 			ERR_FAIL_COND(touch.size() != p_points.size());
 
+			if (touch.size() == 1) {
+				Point2 d = (p_points[0].pos - touch.write[0].pos);
+				if (fabs(d.x) > PAN_GESTURE_MIN_DELTA || fabs(d.y) > PAN_GESTURE_MIN_DELTA) {
+					Ref<InputEventPanGesture> ev;
+					ev.instance();
+					ev->set_position(p_points[0].pos);
+					ev->set_delta(d);
+					input->parse_input_event(ev);
+					touch.write[0].pos = p_points[0].pos;
+				}
+			} else if (touch.size() == 2) {
+				Point2 v0 = touch[1].pos - touch[0].pos;
+				float l0 = (v0.x * v0.x) + (v0.y * v0.y);
+				if (l0 != 0.0) {
+					Point2 v1 = p_points[1].pos - p_points[0].pos;
+					float l1 = (v1.x * v1.x) + (v1.y * v1.y);
+					float f = (l1 / l0);
+					if (fabs(f - 1.0) > MAGNIFY_GESTURE_MIN_FACTOR) {
+						Ref<InputEventMagnifyGesture> ev;
+						ev.instance();
+						ev->set_position(p_points[0].pos + v1 / 2);
+						ev->set_factor(sqrt(f));
+						input->parse_input_event(ev);
+						touch.write[0].pos = p_points[0].pos;
+						touch.write[1].pos = p_points[1].pos;
+					}
+				}
+			}
+
 			for (int i = 0; i < touch.size(); i++) {
 
 				int idx = -1;
@@ -420,7 +452,7 @@ void OS_Android::process_touch(int p_what, int p_pointer, const Vector<TouchPos>
 				ERR_CONTINUE(idx == -1);
 
 				if (touch[i].pos == p_points[idx].pos)
-					continue; //no move unncesearily
+					continue; //no unnecessary move
 
 				Ref<InputEventScreenDrag> ev;
 				ev.instance();