Module Duplex.Canvas
Employed by the UIComponents to represent their visual state
The canvas is a two-dimensional table of CanvasPoints which can be resized.
Each CanvasPoint specifies both the visual appearance of a button (via color or text), as well as any sort of value that the UIComponent might define.
Also, the canvas is the layer we perform our updates "through". By checking the "delta", we can decide if something has actually changed before the update is performed.
Think of it as pre-optimization - both cabled MIDI and wireless devices are capable of choking or skipping messages.
Functions
| __init (device) | Initialize the Canvas class |
| set_size (width, height) | Call whenever the size of the parent UIComponent changes |
| write (point, x, y) | Write a single point to the canvas at the provided x/y coordinates |
| fill (point) | Fill/flood entire canvas with given point |
| check_delta (point, x, y) | If point is different from existing value, mark the canvas as changed both color, text and value are considered when doing the comparison |
| clear_delta () | After the display has finished drawing the object, this is called to clear the delta buffer and mark the canvas as unchanged |
Tables
| self.delta | (table) difference buffer, cleared on each update |
| self.buffer | (table) the current, complete representation |
| self.clear | table of extraneous points that should be cleared on next update created when the canvas is reduced in size, and contains just a simple set of booleans (the Display class will create the empty points when needed) |
Fields
| self.has_changed | (bool) flag when we need to update the display |
| self.width | (int) canvas width |
| self.height | (int) canvas height |
Functions
- __init (device)
-
Initialize the Canvas class
Parameters:
- device (Device)
- set_size (width, height)
-
Call whenever the size of the parent UIComponent changes
Parameters:
- width (int)
- height (int)
- write (point, x, y)
-
Write a single point to the canvas at the provided x/y coordinates
Parameters:
- point (Duplex.CanvasPoint)
- x (int)
- y (int)
- fill (point)
-
Fill/flood entire canvas with given point
Parameters:
- point (Duplex.CanvasPoint)
- check_delta (point, x, y)
-
If point is different from existing value, mark the canvas as changed
both color, text and value are considered when doing the comparison
Parameters:
- point (Duplex.CanvasPoint)
- x (int)
- y (int)
- clear_delta ()
- After the display has finished drawing the object, this is called to clear the delta buffer and mark the canvas as unchanged
Tables
- self.delta
-
(table) difference buffer, cleared on each update
Fields:
- {
- self.buffer
-
(table) the current, complete representation
Fields:
- {
- self.clear
- table of extraneous points that should be cleared on next update created when the canvas is reduced in size, and contains just a simple set of booleans (the Display class will create the empty points when needed)