Add the heap allocation feature

Some platforms (like ESP32) have a limited stack size, but a bigger heap
which can range 2-4MBytes for spiram. In such platforms it's impossible
to allocate most of the displays in the stack, but it's possible to
get them heap allocated (as long as we are compiling with std).

This commit adds the "heap" feature, disabled by default, which will
import std, and add the ability to create the display graphics in
heap instead of the stack.

Cargo.toml

@@ -52,6 +52,9 @@ required-features = ["linux-dev"]
 # Remove the linux-dev feature to build the tests on non  unix systems
 default = ["graphics", "linux-dev"]
 
+# Allow allocating displays from heap instead of the stack
+heap = []
+
 graphics = ["embedded-graphics-core"]
 linux-dev = []
 

src/epd1in54/graphics.rs

@@ -5,6 +5,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 1in54 EPD
 ///
 /// Can also be manuall constructed:
@@ -24,6 +27,17 @@ impl Default for Display1in54 {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display1in54 {
+    fn new() -> Box<Self> {
+        Box::<Display1in54>::new(Display1in54 {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value();
+                WIDTH as usize * HEIGHT as usize / 8],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display1in54 {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;

src/epd1in54b/graphics.rs

@@ -3,6 +3,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 1in54 EPD
 ///
 /// Can also be manually constructed and be used together with VarDisplay
@@ -21,6 +24,17 @@ impl Default for Display1in54b {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display1in54b {
+    fn new() -> Box<Self> {
+        Box::<Display1in54b>::new(Display1in54b {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value();
+                WIDTH as usize * HEIGHT as usize / 8],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display1in54b {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;

src/epd1in54c/graphics.rs

@@ -3,6 +3,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 1in54c EPD
 ///
 /// Can also be manually constructed and be used together with VarDisplay
@@ -20,6 +23,16 @@ impl Default for Display1in54c {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display1in54c {
+    fn new() -> Box<Self> {
+        Box::<Display1in54c>::new(Display1in54c {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value(); NUM_DISPLAY_BITS as usize],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display1in54c {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;

src/epd2in13_v2/graphics.rs

@@ -4,6 +4,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 2in13 v2 EPD
 ///
 /// Can also be manually constructed:
@@ -23,6 +26,17 @@ impl Default for Display2in13 {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display2in13 {
+    fn new() -> Box<Self> {
+        Box::<Display2in13>::new(Display2in13 {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value();
+                buffer_len(WIDTH as usize, HEIGHT as usize)],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display2in13 {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;

src/epd2in13bc/graphics.rs

@@ -3,6 +3,9 @@ use crate::epd2in13bc::{DEFAULT_BACKGROUND_COLOR, HEIGHT, NUM_DISPLAY_BITS, WIDT
 use crate::graphics::{DisplayColorRendering, DisplayRotation, TriDisplay};
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 2.13" b/c EPD
 ///
 /// Can also be manually constructed and be used together with VarDisplay
@@ -23,6 +26,16 @@ impl Default for Display2in13bc {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display2in13bc {
+    fn new() -> Box<Self> {
+        Box::<Display2in13bc>::new(Display2in13bc {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value(); 2 * NUM_DISPLAY_BITS as usize],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display2in13bc {
     type Color = TriColor;
     type Error = core::convert::Infallible;

src/epd2in7b/graphics.rs

@@ -3,6 +3,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 2in7B EPD
 ///
 /// Can also be manuall constructed:
@@ -22,6 +25,17 @@ impl Default for Display2in7b {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display2in7b {
+    fn new() -> Box<Self> {
+        Box::<Display2in7b>::new(Display2in7b {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value();
+                WIDTH as usize * HEIGHT as usize / 8],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display2in7b {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;

src/epd2in9/graphics.rs

@@ -3,6 +3,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Display with Fullsize buffer for use with the 2in9 EPD
 ///
 /// Can also be manuall constructed:
@@ -22,6 +25,17 @@ impl Default for Display2in9 {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display2in9 {
+    fn new() -> Box<Self> {
+        Box::<Display2in9>::new(Display2in9 {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value();
+                WIDTH as usize * HEIGHT as usize / 8],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display2in9 {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;

src/epd2in9_v2/graphics.rs

@@ -3,6 +3,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Display with Fullsize buffer for use with the 2in9 EPD V2
 ///
 /// Can also be manuall constructed:
@@ -22,6 +25,17 @@ impl Default for Display2in9 {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display2in9 {
+    fn new() -> Box<Self> {
+        Box::<Display2in9>::new(Display2in9 {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value();
+                WIDTH as usize * HEIGHT as usize / 8],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display2in9 {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;

src/epd2in9bc/graphics.rs

@@ -3,6 +3,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 2in9b/c EPD
 ///
 /// Can also be manually constructed and be used together with VarDisplay
@@ -20,6 +23,16 @@ impl Default for Display2in9bc {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display2in9bc {
+    fn new() -> Box<Self> {
+        Box::<Display2in9bc>::new(Display2in9bc {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value(); NUM_DISPLAY_BITS as usize],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display2in9bc {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;

src/epd4in2/graphics.rs

@@ -3,6 +3,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 4in2 EPD
 ///
 /// Can also be manuall constructed:
@@ -22,6 +25,17 @@ impl Default for Display4in2 {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display4in2 {
+    fn new() -> Box<Self> {
+        Box::<Display4in2>::new(Display4in2 {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value();
+                WIDTH as usize * HEIGHT as usize / 8],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display4in2 {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;

src/epd5in65f/graphics.rs

@@ -1,6 +1,10 @@
 use crate::color::OctColor;
 use crate::epd5in65f::{DEFAULT_BACKGROUND_COLOR, HEIGHT, WIDTH};
 use crate::graphics::{DisplayRotation, OctDisplay};
+
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 use embedded_graphics_core::prelude::*;
 
 /// Full size buffer for use with the 5in65f EPD
@@ -22,6 +26,17 @@ impl Default for Display5in65f {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display5in65f {
+    fn new() -> Box<Self> {
+        Box::<Display5in65f>::new(Display5in65f {
+            buffer: [OctColor::colors_byte(DEFAULT_BACKGROUND_COLOR, DEFAULT_BACKGROUND_COLOR);
+                WIDTH as usize * HEIGHT as usize / 2],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display5in65f {
     type Color = OctColor;
     type Error = core::convert::Infallible;

src/epd5in83b_v2/graphics.rs

@@ -4,6 +4,9 @@ use crate::graphics::{DisplayColorRendering, DisplayRotation};
 use crate::prelude::TriDisplay;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 5in83 EPD
 ///
 /// Can also be manually constructed:
@@ -26,6 +29,20 @@ impl Default for Display5in83 {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display5in83 {
+    fn new() -> Box<Self> {
+        let mut display = Box::<Display5in83>::new(Display5in83 {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value(); 2 * NUM_DISPLAY_BITS as usize],
+            rotation: DisplayRotation::default(),
+        });
+        // We need to invert chromatic part to black so it will be render white
+        let offset = display.chromatic_offset();
+        display.buffer[offset..].fill(0x00);
+        display
+    }
+}
+
 impl DrawTarget for Display5in83 {
     type Color = TriColor;
     type Error = core::convert::Infallible;

src/epd7in5/graphics.rs

@@ -3,6 +3,9 @@ use crate::graphics::{Display, DisplayRotation};
 use embedded_graphics_core::pixelcolor::BinaryColor;
 use embedded_graphics_core::prelude::*;
 
+#[cfg(feature = "heap")]
+use {crate::graphics::HeapAllocated, std::boxed::Box};
+
 /// Full size buffer for use with the 7in5 EPD
 ///
 /// Can also be manually constructed:
@@ -22,6 +25,17 @@ impl Default for Display7in5 {
     }
 }
 
+#[cfg(feature = "heap")]
+impl HeapAllocated for Display7in5 {
+    fn new() -> Box<Self> {
+        Box::<Display7in5>::new(Display7in5 {
+            buffer: [DEFAULT_BACKGROUND_COLOR.get_byte_value();
+                WIDTH as usize * HEIGHT as usize / 8],
+            rotation: DisplayRotation::default(),
+        })
+    }
+}
+
 impl DrawTarget for Display7in5 {
     type Color = BinaryColor;
     type Error = core::convert::Infallible;