JavaFX controls have large size on Raspberry Pi

[Kevin Rushforth]

Another thing to check is that the reported DPI of the screen is correct.

-- Kevin


On 4/20/2020 1:25 PM, David Grieve wrote:
> The sizes of controls are controlled by CSS styles. Things like borders, backgrounds, padding, insets, all of
> that defaults to the styles in a stylesheet. Most sizes are 'em' units, meaning they are relative to the size
> of the font. JavaFX CSS will use the Font.getDefault() font size if there is no font explicitly set in either the
> styles or in the application code.
>
> I would start by looking at what Font.getDefault().getSize() returns since everything should be based off that.
> It could also be an issue with the default stylesheets themselves.
>
> -----Original Message-----
> From: openjfx-dev <openjfx-dev-bounces at openjdk.java.net> On Behalf Of Alexander Scherbatiy
> Sent: Monday, April 20, 2020 2:16 PM
> To: openjfx-dev at openjdk.java.net
> Subject: [EXTERNAL] JavaFX controls have large size on Raspberry Pi
>
> Hello,
>
> I run a simple JavaFX application which shows a button with jdk 14.0.1 on Raspberry Pi and the drawn button has large size.
>
> This is because of the algorithm which is used by
> PrismFontFactory.getSystemFontSize() method [1] to select a system font size.
> If a system is embedded then the font size is calculated as
>
>       int screenDPI = Screen.getMainScreen().getResolutionY();
>       systemFontSize = ((float) screenDPI) / 6f; // 12 points
>
> and the system is detected as embedded because the armv6hf architecture is defined as embedded in the armv6hf.gradle file [2].
>
> Raspberri Pi can work both with small touch displays and with big monitors. It looks like Raspberry Pi should support two modes for font size calculation: one for small screens and another for large.
>
> I would like to contribute a fix for this but I do not know how the right fix could look like.
> Should there be a special screen size so for smaller screens the font is is proportional to the screen size and for bigger screens the font size is fixed?
> Is there a way to check that used screen is from embedded device?
> May be it should be solved in different way?
>
> [1]
> https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fopenjdk%2Fjfx%2Fblob%2Fec8608f39576035d41e8e532e9334b979b859543%2Fmodules%2Fjavafx.graphics%2Fsrc%2Fmain%2Fjava%2Fcom%2Fsun%2Fjavafx%2Ffont%2FPrismFontFactory.java%23L1944&data=02%7C01%7CDavid.Grieve%40microsoft.com%7Cc0b7e923fe4346bf947608d7e55746f0%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637230035326172309&sdata=rEz4bxNE07aW5f22AXWPRLNffwoIixvNxJopLM%2Bfbi4%3D&reserved=0
> [2]
> https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fopenjdk%2Fjfx%2Fblob%2Fec8608f39576035d41e8e532e9334b979b859543%2FbuildSrc%2Farmv6hf.gradle%23L182&data=02%7C01%7CDavid.Grieve%40microsoft.com%7Cc0b7e923fe4346bf947608d7e55746f0%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637230035326172309&sdata=Fv2sKXwfwuo6JsD0CyeoF6iDmq8rDk5goPCsK31p1Sk%3D&reserved=0
>
> JavaFX application:
> ----------------------------
> import javafx.application.Application;
> import javafx.event.ActionEvent;
> import javafx.event.EventHandler;
> import javafx.scene.Scene;
> import javafx.scene.control.Button;
> import javafx.scene.layout.StackPane;
> import javafx.stage.Stage;
>
> public class ButtonFX extends Application {
>       public static void main(String[] args) {
>           launch(args);
>       }
>
>       @Override
>       public void start(Stage primaryStage) {
>           primaryStage.setTitle("Hello World!");
>       Button button = new Button("Hello, World!");
>
>           StackPane root = new StackPane();
>           root.getChildren().add(button);
>           primaryStage.setScene(new Scene(root, 300, 250));
>           primaryStage.show();
>       }
> }
> ----------------------------
>
> Thanks,
> Alexander.
>
>