Resizable Side Window

Question

Is there any way to create a child window that is resizable only on the right edge and covers up a part of the left side of the parent window? Similar to that of Firefox's History panel.

Answer 1

There is no way to do that in one strike AFAIK. However, you can create a child window as usual and use GetWindowRect() to get dimensions of the bounding rectangle (in this case, we are interested in top, bottom, and right of RECT structure); then intercept the WM_MOUSEMOVE message and keep monitoring the current x & y mouse coordinate from lParam parameter;

If current mouse position is at the right side of the window box, call LoadCursor() or LoadImage() to set the cursor shape to IDC_SIZEWE; then use SetCapture() and ReleaseCapture() to listen to drag-drop mouse event, and use SetWindowPos() to set new size of the window.