DPI change support for offscreen rendering.

[sat]

I have windows app using cef (2704) to render page into the buffer. What exact steps must be made on WM_DPICHANGED message ?
I am doing next:
1. Calc new scale factor (float(HIWORD(wParam)) / USER_DEFAULT_SCREEN_DPI);
2. Call Browser->Host->NotifyScreenInfoChanged()
3. And my GetScreenInfo function is:

Code: Select all

bool
CefClientHandler::GetScreenInfo(
   CefRefPtr<CefBrowser> browser, CefScreenInfo& screen_info)
{
   screen_info.device_scale_factor = myScaleFactor;
   return true;
}


It seems to work, but I am not sure if this a right way to go ? Any suggestions/advises ?

[magreenblatt]

Seems fine.

[sat]

Render works well but mouse event is weird.
E.g. I have a window with sized 100x100. After I change scale factor to 1.5 the window is resized to 150x150.
In JS windows.screen has same new size (150x150) and mouse events has right coords (0-150) but any HTML element inside has old coords/sizes. div at 50,50 with size 10,10 will render perfectly at 75,75 as 15,15 but it's mouseover event will be toggled only when mouse is at 50,50,10,10 and div.getBoundingClientRect() returns not scaled size/coords.
How this shall be handled ? anything beside dividing mouse coords on scale factor ?

[magreenblatt]

Scale factor affects device coordinates. Browser content still operates at standard logical coordinates. If you want larger browser content you should use the zoom function.