Struct mini_gl_fb::MiniGlFb

pub struct MiniGlFb {
    pub internal: Internal,
}

Main wrapper type.

Any fields accessed through internal are not considered a public API and may be subject to breaking API changes. Only access this field as a last resort if the MiniGlFb API fails to fit your exact use case.

Public methods of Internal are considered stable, but may be more complicated to use.

Basic Usage

See the update_buffer and persist methods.

Fields

internal: Internal

Implementations

impl MiniGlFb

pub fn update_buffer<T>(&mut self, image_data: &[T])

Updates the backing buffer and draws immediately (swaps buffers).

The main drawing function.

Panics

Panics if the size of the buffer does not exactly match the correct size of the texture data required based on the buffers format.

pub fn redraw(&mut self)

pub fn use_post_process_shader(&mut self, source: &str)

Use a custom post process shader written in GLSL (version 330 core).

The interface is unapologetically similar to ShaderToy's. It works by inserting your code (it is implemented as literal substitution) into a supplied fragment shader and calls a function main_image that it assumes you define.

Example usage

The behavior of the default fragment shader can be emulated by the following:

fb.use_post_process_shader("
    void main_image( out vec4 r_frag_color, in vec2 v_uv ) {
        r_frag_color = texture(u_buffer, v_uv);
    }
");

Regardless of the format of your buffer, the internal texture is always stored as RGBA, so sampling u_buffer will yield a vec4 representing an RGBA color. The built in grayscale shader, for instance, only stores Red components, and then uses the red component for the green and blue components to create gray.

The output color is determined by the value of the first output parameter, r_frag_color. Your buffer is accessible as a 2D sampler uniform named u_buffer. The first input parameter v_uv is a vec2 UV coordinate. UV (0, 0) represents the bottom left of the screen and (1, 1) represents the top right.

An API for exposing more built in and custom uniforms is planned, along with support for an arbitrary number of render targets and possibly more user supplied textures.

pub fn change_buffer_format<T: ToGlType>(&mut self, format: BufferFormat)

Changes the format of the image buffer.

OpenGL will interpret any missing components as 0, except the alpha which it will assume is 255. For instance, if you set the format to BufferFormat::RG, OpenGL will render every pixel reading the two values you passed for the first two components, and then assume 0 for the blue component, and 255 for the alpha.

If you want to render in grayscale by providing a single component for each pixel, set the buffer format to BufferFormat::R, and call use_grayscale_shader (which will replace the fragment shader with one that sets all components equal to the red component).

The type T does not affect how the texture is sampled, only how the buffer you pass is interpreted. Since there is no way exposed to change the internal format of the texture, (for instance if you wanted to make it an HDR image with floating point components) only the types u8 and i8 are supported. Open an issue if you have a use case for other types.

Example

use mini_gl_fb::BufferFormat;

fb.change_buffer_format::<u8>(BufferFormat::R);
fb.use_grayscale_shader();

pub fn resize_buffer(&mut self, buffer_width: u32, buffer_height: u32)

Resizes the buffer.

This does not affect the size of the window. The texture will be scaled to fit.

pub fn use_grayscale_shader(&mut self)

Switch to a shader that only uses the first component from your buffer.

This does not switch to a shader which converts RGB(A) images to grayscale, for instance, by preserving percieved luminance.

pub fn resize_viewport(&mut self, width: u32, height: u32)

Set the size of the OpenGL viewport (does not trigger a redraw).

For high DPI screens this is the physical size of the viewport.

This does not resize the window or image buffer, only the area to which OpenGL draws. You only need to call this function when you are handling events manually and have a resizable window.

You will know if you need to call this function, as in that case only part of the window will be getting drawn, typically after an update.

pub fn set_resizable(&mut self, resizable: bool)

Set whether or not the window is resizable.

Please note that if you are handling events yourself that you need to call resize_viewport when the window is resized, otherwise the buffer will only be drawn to a small portion of the window.

pub fn persist<ET: 'static>(&mut self, event_loop: &mut EventLoop<ET>)

Keeps the window open until the user closes it.

Supports pressing escape to quit. Automatically scales the rendered buffer to the size of the window if the window is resiable (but this does not resize the buffer).

pub fn persist_and_redraw<ET: 'static>(
    &mut self,
    event_loop: &mut EventLoop<ET>,
    redraw: bool
)

persist implementation.

When redraw is true, redraws as fast as possible. This function is primarily for debugging.

See persist method documentation for more info.

pub fn glutin_handle_basic_input<ET: 'static, F: FnMut(&mut Framebuffer, &mut BasicInput) -> bool>(
    &mut self,
    event_loop: &mut EventLoop<ET>,
    handler: F
)

Provides an easy interface for rudimentary input handling.

Automatically handles close events and partially handles resizes (the caller chooses if a redraw is necessary; and the window will only actually physically change size if it is a resizable window).

Polls for window events and summarizes the input events for you each frame. See BasicInput for the information that is provided to you. You will need to use some glutin types (which just wraps the crate winit's input types), so glutin is re-expoted by this library. You can access it via use mini_gl_fb::glutin.

You can cause the handler to exit by returning false from it. This does not kill the window, so as long as you still have it in scope, you can actually keep using it and, for example, resume handling input but with a different handler callback.

pub fn glutin_breakout(self) -> GlutinBreakout

Need full access to Glutin's event handling? No problem!

Hands you the window we created, so you can handle events however you want, and the Framebuffer, so you can still draw easily!

IMPORTANT: You should make sure to render something before swapping buffers or the window may flash violently. You can call fb.redraw() directly before if you are unsure that an OpenGL draw call was issued. fb.update_buffer will typically issue a draw call.