deadfrog-lib

A simple graphics, keyboard and mouse library with a C interface.

Deadfrog Lib is a collection of simple, portable functions to create a window, get keyboard and mouse input and provide various 2D drawing primitives. It was created due to the frustration I found in just getting a simple interactive program up and running on a PC. The PC should be as easy to program as my ZX Spectrum was in 1982.

It is CPU based and makes no attempt to use the GPU.

It currently supports Windows and Linux/X11.

Functions include

• Window create/destroy.
• 32-bit RGBA bitmap creation.
• Fast software based drawing routines (lines, curves, ellipses, polygons, text, bilinear filtered stretched blit etc).
• Wait for vsync (or wait for desktop compositor to be ready for another frame).
• Alpha blending support.
• Anti-aliased polygon drawing.
• Mouse and keyboard input.
• Load and save BMP files.

Advantages

• Simple API. Simple source code.
• Depends on no third-party libraries.
• It's tiny. Less than 6000 lines of code.
• Reliable results. If the output looks correct on your machine, it will on other peoples', regardless of how buggy their GPU drivers are.
• You can produce a single binary that will work on many different Linux distros (because it doesn't even depend on xlib or xcb).
• Easy to debug. Unlike OpenGl/DirectX etc, you can step through all the code in the debugger to see why your rendering code isn't working.
• Written in C++ with a C interface (to make it easy to use from other languages).
• Permissive BSD licence.
• Easy to port to other platforms.

Disadvantages

The library does not make use of the GPU. All the rendering is done by the CPU into bitmaps held in main memory. With modern CPU speeds for many applications this is easily fast enough but obviously it is not as fast as a GPU. I'd use a GPU based library if I needed lots of alpha blending or any non-trivial 3D rendering.

Simplifying Assumptions

To keep the code simple, Deadfrog Lib makes the following assumptions:

• Only 32-bit per pixel is supported.
• The display is always double buffered. All rendering occurs to a bitmap in main memory. This can then be blitted to the screen/window very quickly.

Performance

Below is some performance data of various functions rendering to an in-memory frame buffer. Nothing is visible on the screen. The frame buffer would need to be blitted to the screen for the results to be visible. (Performance of blitting the frame buffer to the screen on my Windows box is around 6 billion pixels per second - eg blitting 1920x1200 to the screen 60 times per second results in about 2% CPU load.)

Running on Windows 10 on a single core of an Intel Core i3 530 @ 2.93 GHz, built with MSVC 2013, targetting x64:

FUNCTION        UNIT                    Rate        NOTES
-------------------------------------------------------------------------------------
Put pixel       million per sec         125
Put pixel       million per sec         95          Alpha blended
Line draw       million pixels per sec  650
Rectangle fill  million pixels per sec  5700
Text render     million chars per sec   41          7x13 pixel bitmap font
Swap buffers    number per sec          1260        Bitmap size 1280x1024

Hello World Example

#include "df_bitmap.h"
#include "df_font.h"
#include "df_window.h"
#include "fonts/df_mono.h"

int main() { 
    DfWindow *win = CreateWin(800, 600, WT_WINDOWED_RESIZEABLE, "Hello World Example");
    g_defaultFont = LoadFontFromMemory(df_mono_7x13, sizeof(df_mono_7x13));

    while (!win->windowClosed && !win->input.keys[KEY_ESC]) {
        BitmapClear(win->bmp, g_colourBlack);
        InputPoll(win);

        unsigned x = 100;
        unsigned y = 100;
        DfColour col = g_colourWhite;
        DrawTextSimple(g_defaultFont, col, win->bmp, x, y, "Hello World!");

        // Draw frames per second counter
        DrawTextRight(g_defaultFont, g_colourWhite, win->bmp, win->bmp->width - 5, 0, "FPS:%i", win->fps);

        UpdateWin(win);
        WaitVsync();
    }
}

Projects using Deadfrog-lib

• Code Trowel - A programmer's text editor.
• Sound Shovel - A very incomplete WAV file editor.