Two new tools added to the Level Editor:
* Pan Tool: left-click to scroll the level around safely.
* Text Tool: write text onto your level.
Features of the Text Tool:
* Can choose from the game's built-in fonts, size and enter the message
you want to write.
* The mouse cursor previews the text when hovered over the level.
* Click to "stamp" the text onto your level. The currently selected
color swatch will be used to color the text in.
* Adds two new fonts: Azulian.ttf and Rive.ttf that can be selected in
the Text Tool.
Some implementation notes:
* Added package native/engine_sdl.go that handles the lower-level
SDL2_TTF logic to rasterize the text into a black&white image.
* WASM not supported yet (if the game even still built for WASM);
native/engine_wasm.go stubs out the TextToImage() call with a "not
supported" error just in case.
Other changes:
* New Toolbar icons: they are 24x24 instead of 32x32 to make more room
for more tools.
* The toolbar now shows two buttons per row for a more densely packed
layout. For very narrow screen widths (< 600px) the default Vertical
Toolbar layout will use one-button-per-row to not eat too much screen
real estate.
* In the Horizontal Toolbars layout there are 2 buttons per column.
* Toolbar has icon buttons for the Pencil Tool, Line Tool, Rect Tool,
Actor Tool and Link Tool.
* Remove the tab buttons from the top of the Palette window. The palette
tab is now toggled between Swatches and Doodads by the tool selected
on the tool bar, instead of the tab buttons setting the tool.
* Remove the "Link Doodads" button from the Doodad Palette. The Link
Tool has its own dedicated toolbar button with the others.
