Changing DPI scaling size of display make Qt application's font size get rendered bigger

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I have created some GUI application using Qt. My GUI application contains controls like push button and radio button. When I run the application, buttons and fonts inside button looks normal. When I change the DPI scaling size of display from 100% to 150% or 200%, font size of controls rendered bigger but not control size (pushbutton, radio button) irrespective of resolution. Due to this the text inside controls were cut off. please see the attached image.

Qt application look when DPI scaling size set to 100%

Qt application look when DPI scaling size set to 100%

Qt application look when DPI scaling size set to 200%

Qt application look when DPI scaling size set to 200%

I am running my application in some tablets also. In tablets, DPI scale value should be more than 150% else everything will be shown very small.

I searched in the web for creating UI application in Qt irrespective of resolution and DPI scale value but no luck. So I am posting my questing here. Please let me know if there is some way to get rid of this.

resolution dpi qt user-interface c++
6 Answers

Here is a workaround:

Create a file qt.conf and add these lines to it.

[Platforms]
WindowsArguments = dpiawareness=0

Put this file in the application binary folder. That's all. It will work well but only issue is that the look will not be that crisp. For delivering it to the customer, add this file where you have your dependency files & while creating setup, like normally you run your dependency files, run this same as well.

user_142090590

There are several options when dealing with high-resolution displays:

  1. Do nothing and develop in high resolution. Eventually, a higher resolution becomes a new standard, everybody will get 13-15-17 inches. It did work in the 2000th, didn't it?
  2. Leave it to the OS. For example, Windows has a special compatibility setting which scales everything to correct size, while keeping the application think that it renders of a low-resolution display. This is called DPI Unaware on Windows.
  3. Try to use Qt capabilities, QT_AUTO_SCREEN_SCALE_FACTOR=0, QT_SCALE_FACTOR=1.
  4. Use a little bit of help from Qt by setting QT_AUTO_SCREEN_SCALE_FACTOR to 1 or a correspondent AA_EnableHighDpiScaling attribute (introduced in Qt 5.6). This will scale widget sizes relative to the font size, so you only need to deal with raster images.
  5. Turn off AA_EnableHighDpiScaling and rethink all your pixel sizes by making them relative to the font size or multiplying them over the device pixel ratio.
  6. An improvement over a previous step: take into an account the device pixel ratio on every display, so that UI is scaled appropriately when you move it to another display.

Sources:

user_990240

There are many ways.

  • one of them is to have reference (height, width and DPI) and when you run your application on a different setup all you need is to get height, width and the logical dots per inch
  • you can use qreal dpi = QGuiApplication::primaryScreen()->logicalDotsPerInch();

and then you calculate the new font size by multiplying it with the calculated ratio.

qreal refDpi = 216.;
qreal refHeight = 1776.;
qreal refWidth = 1080.;
QRect rect = QGuiApplication::primaryScreen()->geometry();
qreal height = qMax(rect.width(), rect.height());
qreal width = qMin(rect.width(), rect.height());
qreal dpi = QGuiApplication::primaryScreen()->logicalDotsPerInch();
m_ratio = qMin(height/refHeight, width/refWidth);
m_ratioFont = qMin(height*refDpi/(dpi*refHeight), width*refDpi/(dpi*refWidth));
  • the second way, which is extremely simple, more productive and personally I use it, is simply by using stylesheets!!, and the font size won't change by your DPI scaling.

you can use font property like that for example

font: bold italic large "Times New Roman";
user_170720780
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