SplashKit Interface Functionality

[WhyPenguins]

This PR is dependent/related to a couple of others, please make sure they get merged together! See bottom for details

Overview

This PR adds the ability to easily create and style user interfaces with SplashKit programmatically, with an immediate mode GUI (IMGUI) style API. It uses the MicroUI library to handle widget logic, and SplashKit's in-built routines to handle input/rendering.

It is hoped that this will allow students to begin visualizing variables using the interface functions, and develop more interactive graphical programs with ease.

The API has been designed such that only a basic understanding of calling functions with parameters, and storing the returned values in variables is required - unlike most IMGUI APIs, pointers and so on are avoided.

Demo

See below for a demo of the interfaces that can be created:

Simple usage example

#include "splashkit.h"

int main()
{
    // open a window
    open_window("My Interface!", 800, 600);

    // main loop
    while (!quit_requested())
    {
        // get user events
        process_events();

        // clear screen
        clear_screen(COLOR_WHITE);

        // place button on screen and test if clicked
        if (button("Write To Terminal!", rectangle_from(300, 260, 200, 24)))
        {
            write_line("Hello there!");
        }

        // finally draw interface, then refresh screen
        draw_interface();

        refresh_screen();
    }

    // program ends, and the window closes
    return 0;
}

Main Changes

• Includ MicroUI in repository and integrat into input handling/rendering.
• Create interface_driver backend for abstracting out MicroUI to a degree.
• Expose UI elements, layout, and styling options to the user facing API.

With some miscellaneous additions:

• Add user facing get_system_font() function
• Add internal sk_draw_blurred_rect(...) function
• Add new UI test

Feature overview

• Containers: windows (referred to as 'panels'), popups, insets
• Elements: labels, buttons, bitmap buttons, sliders, check boxes, text boxes, number boxes, HSVA/RGBA color sliders
  • Can be created directly on main window, or auto placed inside containers
  • Can be disabled/enabled
  • Also have 'with_label' versions that provide a label on the left
• Layouting elements: treeviews, columns, headers
• Styling functions
  • Various color customization options
  • Soft shadows from elements/panels
  • Preset interface styles
• Error recovery and reporting
• Documentation for all user facing API functions

Dependencies

Add MicroUI External - splashkit/splashkit-external#6

• Adds the MicroUI dependency, important!

Related PRs

Tutorials on SplashKit's interface functionality - thoth-tech/splashkit.io-starlight#26

• I imagine these will need to be made as a PR to the upstream repo, let me know if so!
• One limitation of these tutorials is that they only have C++ examples. Once this PR is merged and C# binaries produced, it'll be easier for me to add C# examples, so perhaps the tutorials can be merged later once that's done. Or they could be merged along with this PR and C# examples can be added later instead.