Apply the line's shear to the x/y rotation grid

aegisub/src/gl_wrap.cpp

@@ -415,6 +415,17 @@ void OpenGLWrapper::SetRotation(float x, float y, float z) {
 	glRotatef(z, 0.f, 0.f, -1.f);
 }
 
+void OpenGLWrapper::SetShear(float x, float y) {
+	PrepareTransform();
+	float matrix[16] = {
+		1, y, 0, 0,
+		x, 1, 0, 0,
+		0, 0, 1, 0,
+		0, 0, 0, 1
+	};
+	glMultMatrixf(matrix);
+}
+
 void OpenGLWrapper::PrepareTransform() {
 	if (!transform_pushed) {
 		glMatrixMode(GL_MODELVIEW);

aegisub/src/gl_wrap.h

@@ -49,6 +49,7 @@ public:
 	void SetScale(Vector2D scale);
 	void SetOrigin(Vector2D origin);
 	void SetRotation(float x, float y, float z);
+	void SetShear(float x, float y);
 	void ResetTransform();
 
 	void DrawLine(Vector2D p1, Vector2D p2) const;

aegisub/src/visual_tool.cpp

@@ -445,6 +445,17 @@ void VisualToolBase::GetLineRotation(AssDialogue *diag, float &rx, float &ry, fl
 		rz = tag->front().Get(rz);
 }
 
+void VisualToolBase::GetLineShear(AssDialogue *diag, float& fax, float& fay) {
+	fax = fay = 0.f;
+
+	boost::ptr_vector<AssDialogueBlock> blocks(diag->ParseTags());
+
+	if (param_vec tag = find_tag(blocks, "\\fax"))
+		fax = tag->front().Get(fax);
+	if (param_vec tag = find_tag(blocks, "\\fay"))
+		fay = tag->front().Get(fay);
+}
+
 void VisualToolBase::GetLineScale(AssDialogue *diag, Vector2D &scale) {
 	float x = 100.f, y = 100.f;
 

aegisub/src/visual_tool.h

@@ -122,6 +122,7 @@ protected:
 	Vector2D GetLineOrigin(AssDialogue *diag);
 	bool GetLineMove(AssDialogue *diag, Vector2D &p1, Vector2D &p2, int &t1, int &t2);
 	void GetLineRotation(AssDialogue *diag, float &rx, float &ry, float &rz);
+	void GetLineShear(AssDialogue *diag, float& fax, float& fay);
 	void GetLineScale(AssDialogue *diag, Vector2D &scale);
 	void GetLineClip(AssDialogue *diag, Vector2D &p1, Vector2D &p2, bool &inverse);
 	std::string GetLineVectorClip(AssDialogue *diag, int &scale, bool &inverse);

aegisub/src/visual_tool_rotatexy.cpp

@@ -41,6 +41,7 @@ void VisualToolRotateXY::Draw() {
 	// Transform grid
 	gl.SetOrigin(org->pos);
 	gl.SetRotation(angle_x, angle_y, angle_z);
+	gl.SetShear(fax, fay);
 
 	// Draw grid
 	gl.SetLineColour(colour[0], 0.5f, 2);
@@ -178,4 +179,5 @@ void VisualToolRotateXY::DoRefresh() {
 	org->pos = FromScriptCoords(org->pos);
 
 	GetLineRotation(active_line, angle_x, angle_y, angle_z);
+	GetLineShear(active_line, fax, fay);
 }

aegisub/src/visual_tool_rotatexy.h

@@ -27,6 +27,9 @@ class VisualToolRotateXY : public VisualTool<VisualDraggableFeature> {
 	float angle_y = 0.f; /// Current y rotation
 	float angle_z = 0.f; /// Current z rotation
 
+	float fax = 0.f;
+	float fay = 0.f;
+
 	float orig_x = 0.f; ///< x rotation at the beginning of the current hold
 	float orig_y = 0.f; ///< y rotation at the beginning of the current hold