Howto:Creating a Font Browser using Nasal and Canvas

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Status

Last updated 02/2020

Background

No easy way to browse a list of available PUI fonts in the base package in-sim, i.e.: https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Fonts/

Idea

Implement a simple font browser using Nasal and Canvas

Approach

since FlightGear uses OpenSceneGraph, and since OSG supports TXF file, we might be able use Nasal/Canvas to display a list of fonts and even preview them inside fgfs by simply rendering them as a raster image using the canvas image element.

To see for yourself, modify the Canvas image example to point to a font file:

If this works, this can be trivially extended to show a list of all fonts including a preview, by adapting this snippet: Canvas_Snippets#Canvas_ScrollArea

Alternatively, it would be possible to render the menubar completely using the Canvas system: Howto:Making_a_Canvas_Menubar

Proof of Concept

# these are the dimensions of the window to be created
var (width,height) = (320,160);
var title = 'Font Browser (by downpilot)';

# create a new window, dimensions are WIDTH x HEIGHT, using the dialog decoration (i.e. titlebar)
var window = canvas.Window.new([width,height],"dialog")
 .set('title',title);

# adding a canvas to the new window and setting up background colors/transparency
var myCanvas = window.createCanvas().set("background", canvas.style.getColor("bg_color"));

# Using specific css colors would also be possible:
# myCanvas.set("background", "#ffaac0");

# creating the top-level/root group which will contain all other elements/group
var root = myCanvas.createGroup();

# path is relative to $FG_ROOT (base package)
var path = "Fonts/Helvetica.txf";
# create an image child for the texture
var child = root.createChild("image")
    .setFile(path)
    .setTranslation(100, 10)
    .setSize(130, 130); # size of the image

Next

We can adapt the code by using a layout with a vertical scrollArea, so one image per font file can be added/shown: Canvas_Snippets#Canvas_ScrollArea

To populate the vector of file names, we can use the directory() API: 

var fgroot = getprop("/sim/fg-root");
var font_dir = fgroot ~ "/Fonts/";

var files = directory(font_dir);

debug.dump( files );

To only look for specific files, we can split each file name using the dot as separator: 

var myfilename ="Foobar24.txf";

var (basename,extension) = split(".", myfilename);

print("Basename: ", basename);
print("Extension: ", extension);

See also

References

References
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