Re: What is the correct way to response to the wxEVT_DPI_CHANGED event?

Actually my comment about wxWindow::FromDIP is invalid. It shouldn't 
matter if you use wxWindow:: prefix.
I am not sure why using the Reset mode button results in a button with 
the wrong size. I cannot seem to reproduce this.

Maarten

On 30-3-2023 12:01, Maarten Bent wrote:
> Hi,
>
> In most cases you shouldn't have to do anything. The scaling is done 
> internally.
> If your own code has stuff that depend on the DPI, you can handle the 
> event and update things accordingly.
>
> FromDIP converts a device-independent size to the size applicable for 
> the display.
> So if your display has scaling 100% it converts 250x50 to 250x50 
> physical pixels
> If your display has 200% scaling, it converts 250x50 to 500x100 
> physical pixels.
> This ensures that it will look the same on both displays.
>
> In your example on the forum you use the static wxWindow::FromDIP() 
> function. This is incorrect. It will always use the DPI of the main 
> window when creating the control.
> This is why you see the wrong button size when you reset the 
> resolution and the button is recreated.
> You should use member function FromDIP() (without wxWindow::), so it 
> will use the DPI of the display that the window is shown on.
>
> wxDisplay::OnResetMode is definitely not needed for DPI changes.
>
> Maarten
>
> On 30-3-2023 07:52, AsmWarrior wrote:
>> Hi, when the application receive a wxEVT_DPI_CHANGED event, how can 
>> it response to the event?
>>
>> I looked at the wxWidgets' sample code "display", it looks like it 
>> does nothing, but just show some text in the status bar:
>>
>> void MyFrame::OnDPIChanged(wxDPIChangedEvent& event)
>> {
>>     wxLogStatus(this, "DPI changed: was %d*%d, now %d*%d",
>>                 event.GetOldDPI().x, event.GetOldDPI().y,
>>                 event.GetNewDPI().x, event.GetNewDPI().y);
>>
>>     event.Skip();
>> }
>>
>> But if we need to layout the UIs, do we need to call the ResetMode() 
>> function of the wxDisplay class?
>>
>> I just search for the "ResetMode" in wxWidgets' github site, I don't 
>> see much usage of this function.
>>
>> In the "display" sample code, this function is called when a wxButton 
>> get clicked.
>>
>> I even did some test about the DPI changing, and I think if 
>> ResetMode() is not called, the layout is wrong, you can see the 
>> discussion and image shots here in the:
>>
>> How does the FromDIP function work under different DPI scaling? — 
>> https://forums.wxwidgets.org/viewtopic.php?p=218156#p218156
>>
>> Any suggestions? Thanks!
>>
>> Asmwarrior
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