From 64da1084a0c9605b10dfe19d4e174c1dec92172c Mon Sep 17 00:00:00 2001
From: papush! <contact@ccolin.fr>
Date: Sat, 27 Nov 2021 14:11:18 +0100
Subject: [PATCH] fix view controls

---
 src/mesh_viewer.cpp | 19 +++++++++++--------
 src/mesh_viewer.h   |  5 ++---
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/mesh_viewer.cpp b/src/mesh_viewer.cpp
index eaebd80..45bb717 100644
--- a/src/mesh_viewer.cpp
+++ b/src/mesh_viewer.cpp
@@ -9,11 +9,12 @@
 MeshViewer::MeshViewer(QWidget *parent) : QOpenGLWidget(parent) {
 	setMouseTracking(true);
 	setFocus();
+	updateViewMatrix();
 }
 
 
 void MeshViewer::updateViewMatrix() {
-	view = trans * zoom * rot;
+	view = zoom * rot * trans;
 }
 
 
@@ -121,7 +122,6 @@ void MeshViewer::updateForReal() {
 void MeshViewer::mousePressEvent(QMouseEvent *e) {
 	if (e->button() & Qt::MiddleButton || e->button() & Qt::RightButton) {
 		mouse_pos = e->pos();
-		trans_start = trans;
 	} else if (e->button() == Qt::LeftButton) {
 		float x = e->x();
 		float y = height() - e->y();
@@ -141,23 +141,26 @@ void MeshViewer::mousePressEvent(QMouseEvent *e) {
 
 void MeshViewer::mouseReleaseEvent(QMouseEvent *e) {
 	(void) e;
-	rot_start = rot;
 }
 
 
 void MeshViewer::mouseMoveEvent(QMouseEvent *e) {
+	QPoint delta = e->pos() - mouse_pos;
+	mouse_pos = e->pos();
 	if (e->buttons() & Qt::MiddleButton) {
-		QPoint delta = e->pos() - mouse_pos;
-		rot = rot_start;
 		rot.rotate(delta.x() / 5., 0, 1, 0);
 		rot.rotate(delta.y() / 5., QVector3D(1, 0, 0) * rot);
 		updateViewMatrix();
 		update();
 	}
 	if (e->buttons() & Qt::RightButton) {
-		trans = trans_start;
-		trans(0, 3) += (e->pos() - mouse_pos).x() / 1000.;
-		trans(1, 3) -= (e->pos() - mouse_pos).y() / 1000.;
+		QMatrix4x4 screen_trans;
+		screen_trans.translate(delta.x() / 1000., -delta.y() / 1000., 0);
+		trans = rot.inverted() * screen_trans * rot * trans;
+		// trans(0, 0) = 1;
+		// trans(0, 1) = 0;
+		// trans(1, 0) = 0;
+		// trans(1, 1) = 1;
 		updateViewMatrix();
 		update();
 	}
diff --git a/src/mesh_viewer.h b/src/mesh_viewer.h
index e626b78..47e044e 100644
--- a/src/mesh_viewer.h
+++ b/src/mesh_viewer.h
@@ -31,9 +31,8 @@ class MeshViewer : public QOpenGLWidget {
 								 0, 1, 0, 0,
 								 0, 0, 1, -1,
 								 0, 0, 0, 1);
-	QMatrix4x4 trans, trans_start;
-	QMatrix4x4 rot, rot_start;
-	QMatrix4x4 view = trans * zoom * rot;
+	QMatrix4x4 rot, trans;
+	QMatrix4x4 view;
 	QPoint mouse_pos;
 	void updateViewMatrix();
 	bool is_initialized = false;