editor: allow reordering tracks by dragging mouse

Previously the only way of reordering tracks were with an
obscure keyboard short-cut. Most users would expect to be
able to do this with the mouse, so we'll allow that.

editor/trackview.cpp

@@ -64,6 +64,8 @@ TrackView::TrackView()
 	
 	editBrush = CreateSolidBrush(RGB(255, 255, 0)); // yellow
 
+	handCursor = LoadCursor(NULL, IDC_HAND);
+
 	clipboardFormat = RegisterClipboardFormat("syncdata");
 	assert(0 != clipboardFormat);
 }
@@ -111,6 +113,19 @@ int TrackView::getScreenX(size_t track) const
 	return int(leftMarginWidth + (track * trackWidth)) - scrollPosX;
 }
 
+inline int divfloor(int a, int b)
+{
+	if (a < 0)
+		return -abs(a) / b - 1;
+	return a / b;
+}
+
+int TrackView::getTrackFromX(int x) const
+{
+	return divfloor(x + scrollPosX - leftMarginWidth, trackWidth);
+}
+
+
 LRESULT TrackView::onCreate()
 {
 //	setFont((HFONT)GetStockObject(SYSTEM_FONT));
@@ -1098,6 +1113,67 @@ LRESULT TrackView::onSize(int width, int height)
 	return FALSE;
 }
 
+LRESULT TrackView::onSetCursor(HWND win, UINT hitTest, UINT message)
+{
+	POINT cpos;
+	GetCursorPos(&cpos);
+	ScreenToClient(hwnd, &cpos);
+	int track = getTrackFromX(cpos.x);
+	if (cpos.y < topMarginHeight &&
+	    track >= 0 && track < int(getTrackCount())) {
+		SetCursor(handCursor);
+		return TRUE;
+	}
+	return DefWindowProc(this->hwnd, WM_SETCURSOR, (WPARAM)hwnd,
+	    MAKELPARAM(hitTest, message));
+}
+
+LRESULT TrackView::onLButtonDown(UINT flags, POINTS pos)
+{
+	int track = getTrackFromX(pos.x);
+	if (pos.y < topMarginHeight &&
+	    track >= 0 && track < int(getTrackCount())) {
+		setEditTrack(track, false);
+		SetCapture(hwnd);
+		anchorTrack = track;
+	}
+	return FALSE;
+}
+
+LRESULT TrackView::onLButtonUp(UINT flags, POINTS pos)
+{
+	ReleaseCapture();
+	setEditTrack(editTrack);
+	return FALSE;
+}
+
+LRESULT TrackView::onMouseMove(UINT flags, POINTS pos)
+{
+	if (GetCapture() == hwnd) {
+		SyncDocument *doc = getDocument();
+		const int posTrack = getTrackFromX(pos.x),
+		    trackCount = getTrackCount();
+
+		if (!doc || posTrack < 0 || posTrack >= trackCount)
+			return FALSE;
+
+		if (posTrack > anchorTrack) {
+			for (int i = anchorTrack; i < posTrack; ++i)
+				doc->swapTrackOrder(i, i + 1);
+			anchorTrack = posTrack;
+			setEditTrack(posTrack);
+			InvalidateRect(hwnd, NULL, FALSE);
+		} else if (posTrack < anchorTrack) {
+			for (int i = anchorTrack; i > posTrack; --i)
+				doc->swapTrackOrder(i, i - 1);
+			anchorTrack = posTrack;
+			setEditTrack(posTrack);
+			InvalidateRect(hwnd, NULL, FALSE);
+		}
+	}
+	return FALSE;
+}
+
 LRESULT TrackView::windowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 {
 	assert(hwnd == this->hwnd);
@@ -1111,6 +1187,15 @@ LRESULT TrackView::windowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
 	case WM_PAINT:   return onPaint();
 	case WM_KEYDOWN: return onKeyDown((UINT)wParam, (UINT)lParam);
 	case WM_CHAR:    return onChar((UINT)wParam, (UINT)lParam);
+	case WM_LBUTTONDOWN:
+		return onLButtonDown((UINT)wParam, MAKEPOINTS(lParam));
+	case WM_LBUTTONUP:
+		return onLButtonUp((UINT)wParam, MAKEPOINTS(lParam));
+	case WM_MOUSEMOVE:
+		return onMouseMove((UINT)wParam, MAKEPOINTS(lParam));
+	case WM_SETCURSOR:
+		return onSetCursor((HWND)wParam, LOWORD(lParam),
+		    HIWORD(lParam));
 
 	case WM_COPY:  editCopy();  break;
 	case WM_CUT:   editCut();   break;

editor/trackview.h

@@ -102,6 +102,10 @@ private:
 	LRESULT onSize(int width, int height);
 	LRESULT onKeyDown(UINT keyCode, UINT flags);
 	LRESULT onChar(UINT keyCode, UINT flags);
+	LRESULT onSetCursor(HWND win, UINT hitTest, UINT message);
+	LRESULT onLButtonDown(UINT flags, POINTS pos);
+	LRESULT onLButtonUp(UINT flags, POINTS pos);
+	LRESULT onMouseMove(UINT flags, POINTS pos);
 
 	void paintTracks(HDC hdc, RECT rcTracks);
 	void paintTopMargin(HDC hdc, RECT rcTracks);
@@ -160,6 +164,7 @@ private:
 	
 	int getScreenY(int row) const;
 	int getScreenX(size_t track) const;
+	int getTrackFromX(int x) const;
 
 	size_t getTrackCount() const
 	{
@@ -184,6 +189,7 @@ private:
 	HPEN rowPen, rowSelectPen;
 	HBRUSH editBrush;
 	HPEN lerpPen, cosinePen, rampPen;
+	HCURSOR handCursor;
 	
 	/* cursor position */
 	int editRow, editTrack;
@@ -199,6 +205,7 @@ private:
 	HWND hwnd;
 	
 	UINT clipboardFormat;
+	int anchorTrack;
 };
 
 ATOM registerTrackViewWindowClass(HINSTANCE hInstance);