Update documentation for built-in renderers

4 files changed, 102 insertions, 3 deletions

diff --git a/ECOSYSTEM.md b/ECOSYSTEM.md
index 82303130..fb0bd56d 100644
--- a/ECOSYSTEM.md
+++ b/ECOSYSTEM.md
@@ -45,7 +45,7 @@ The widgets of a _graphical_ user interface produce some primitives that eventua
 Currently, there are two different official renderers:
 
 - [`iced_wgpu`] is powered by [`wgpu`] and supports Vulkan, DirectX 12, and Metal.
-- [`iced_glow`] is powered by [`glow`] and supports OpenGL 3.3+.
+- [`iced_glow`] is powered by [`glow`] and supports OpenGL 2.1+ and OpenGL ES 2.0+.
 
 Additionally, the [`iced_graphics`] subcrate contains a bunch of backend-agnostic types that can be leveraged to build renderers. Both of the renderers rely on the graphical foundations provided by this crate.
 
diff --git a/README.md b/README.md
index f6917fb4..943c5609 100644
--- a/README.md
+++ b/README.md
@@ -34,7 +34,9 @@ Inspired by [Elm].
   * First-class support for async actions (use futures!)
   * [Modular ecosystem] split into reusable parts:
     * A [renderer-agnostic native runtime] enabling integration with existing systems
-    * A [built-in renderer] supporting Vulkan, Metal, DX11, and DX12
+    * Two [built-in renderers] leveraging [`wgpu`] and [`glow`]
+      * [`iced_wgpu`] supporting Vulkan, Metal and DX12
+      * [`iced_glow`] supporting OpenGL 2.1+ and OpenGL ES 2.0+
     * A [windowing shell]
     * A [web runtime] leveraging the DOM
 
@@ -49,7 +51,10 @@ __iced is currently experimental software.__ [Take a look at the roadmap],
 [Modular ecosystem]: https://github.com/hecrj/iced/blob/master/ECOSYSTEM.md
 [renderer-agnostic native runtime]: https://github.com/hecrj/iced/tree/master/native
 [`wgpu`]: https://github.com/gfx-rs/wgpu-rs
-[built-in renderer]: https://github.com/hecrj/iced/tree/master/wgpu
+[`glow`]: https://github.com/grovesNL/glow
+[`iced_wgpu`]: https://github.com/hecrj/iced/tree/master/wgpu
+[`iced_glow`]: https://github.com/hecrj/iced/tree/master/glow
+[built-in renderers]: https://github.com/hecrj/iced/blob/master/ECOSYSTEM.md#Renderers
 [windowing shell]: https://github.com/hecrj/iced/tree/master/winit
 [`dodrio`]: https://github.com/fitzgen/dodrio
 [web runtime]: https://github.com/hecrj/iced/tree/master/web
@@ -195,6 +200,32 @@ end-user-oriented GUI library, while keeping [the ecosystem] modular:
 [`ggez`]: https://github.com/ggez/ggez
 [the ecosystem]: https://github.com/hecrj/iced/blob/master/ECOSYSTEM.md
 
+## Common problems
+
+1. `Error: GraphicsAdapterNotFound`
+   
+   This occurs when the selected [built-in renderer] is not able to create a context.
+   
+   Often this will occur while using [`iced_wgpu`] as the renderer without
+   supported hardware (needs Vulkan, Metal or DX12). In this case, you could try using the
+   [`iced_glow`] renderer:
+
+   First, check if it works with
+   ```console
+   $ cargo run --features "iced/glow iced/glow_canvas" --package game_of_life
+   ```
+
+   and then use it in your project with
+   ```toml
+   iced = { version = "0.3", default-features = false, features = ["glow"] }
+   ```
+
+   **NOTE:** Chances are you have hardware that supports at least OpenGL 2.1 or OpenGL ES 2.0,
+   but if you don't, right now there's no software fallback, so it means your hardware
+   doesn't support Iced.
+
+[built-in renderer]: https://github.com/hecrj/iced/blob/master/ECOSYSTEM.md#Renderers
+
 ## Contributing / Feedback
 Contributions are greatly appreciated! If you want to contribute, please
 read our [contributing guidelines] for more details.
diff --git a/docker/README.md b/docker/README.md
new file mode 100644
index 00000000..cfb4bab1
--- /dev/null
+++ b/docker/README.md
@@ -0,0 +1,17 @@
+## Build
+To use `cross` to compile for Raspberry Pi you first need to build the docker image.
+Use these commands to build the images needed.
+
+**NOTE:** Run these commands inside the `docker` folder. This is needed since `docker`
+uses surrounding directories as "context" for building the image, which means it'll
+copy the entire `target` directory.
+
+### Raspberry Pi 2/3/4 (32 bits)
+```
+$ docker build -t iced-rs/armv7 -f Dockerfile.armv7-unknown-linux-gnueabihf .
+```
+
+### Raspberry Pi 3/4 (64 bits)
+```
+$ docker build -t iced-rs/aarch64 -f Dockerfile.aarch64-unknown-linux-gnu .
+```
\ No newline at end of file
diff --git a/glow/README.md b/glow/README.md
new file mode 100644
index 00000000..c6b7245e
--- /dev/null
+++ b/glow/README.md
@@ -0,0 +1,51 @@
+# `iced_glow`
+[![Documentation](https://docs.rs/iced_glow/badge.svg)][documentation]
+[![Crates.io](https://img.shields.io/crates/v/iced_glow.svg)](https://crates.io/crates/iced_glow)
+[![License](https://img.shields.io/crates/l/iced_glow.svg)](https://github.com/hecrj/iced/blob/master/LICENSE)
+[![project chat](https://img.shields.io/badge/chat-on_zulip-brightgreen.svg)](https://iced.zulipchat.com)
+
+`iced_glow` is a [`glow`] renderer for [`iced_native`]. This renderer supports OpenGL 3.0+ and OpenGL ES 2.0.
+
+This is renderer is mostly used as a fallback for hardware that doesn't support [`wgpu`] (Vulkan, Metal or DX12).
+
+Currently, `iced_glow` supports the following primitives:
+- Text, which is rendered using [`glow_glyph`]. No shaping at all.
+- Quads or rectangles, with rounded borders and a solid background color.
+- Clip areas, useful to implement scrollables or hide overflowing content.
+- Meshes of triangles, useful to draw geometry freely.
+
+<p align="center">
+  <img alt="The native target" src="../docs/graphs/native.png" width="80%">
+</p>
+
+[documentation]: https://docs.rs/iced_glow
+[`iced_native`]: ../native
+[`glow`]: https://github.com/grovesNL/glow
+[`wgpu`]: https://github.com/gfx-rs/wgpu
+[`glow_glyph`]: https://github.com/hecrj/glow_glyph
+
+## Installation
+Add `iced_glow` as a dependency in your `Cargo.toml`:
+
+```toml
+iced_glow = "0.2"
+```
+
+__Iced moves fast and the `master` branch can contain breaking changes!__ If
+you want to learn about a specific release, check out [the release list].
+
+[the release list]: https://github.com/hecrj/iced/releases
+
+## Current limitations
+
+The current implementation is quite naive, it uses:
+
+- A different pipeline/shader for each primitive
+- A very simplistic layer model: every `Clip` primitive will generate new layers
+- _Many_ render passes instead of preparing everything upfront
+- A glyph cache that is trimmed incorrectly when there are multiple layers (a [`glyph_brush`] limitation)
+
+Some of these issues are already being worked on! If you want to help, [get in touch!]
+
+[get in touch!]: ../CONTRIBUTING.md
+[`glyph_brush`]: https://github.com/alexheretic/glyph-brush