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op: add package op for operations

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Extract operation types from package ui into package op.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
This commit is contained in:
Elias Naur
2019-09-30 15:41:15 +02:00
parent eba1b3a95f
commit 8cf35a1f97
27 changed files with 225 additions and 227 deletions
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ui/doc.go
-58
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@@ -4,64 +4,6 @@
Package ui defines operations buffers, units and common operations
for GUI programs written with the Gio module.
Operations
Gio programs use operations, or ops, for describing their user
interfaces. There are operations for drawing, defining input
handlers, changing window properties as well as operations for
controlling the execution of other operations.
Ops represents a list of operations. The most important use
for an Ops list is to describe a complete user interface update
to a ui/app.Window's Update method.
Drawing a colored square:
import "gioui.org/ui"
import "gioui.org/app"
import "gioui.org/paint"
var w app.Window
ops := new(ui.Ops)
...
ops.Reset()
paint.ColorOp{Color: ...}.Add(ops)
paint.PaintOp{Rect: ...}.Add(ops)
w.Update(ops)
State
An Ops list can be viewed as a very simple virtual machine: it has an implicit
mutable state stack and execution flow can be controlled with macros.
The StackOp saves the current state to the state stack and restores it later:
ops := new(ui.Ops)
var stack ui.StackOp
// Save the current state, in particular the transform.
stack.Push(ops)
// Apply a transform to subsequent operations.
ui.TransformOp{}.Offset(...).Add(ops)
...
// Restore the previous transform.
stack.Pop()
The MacroOp records a list of operations to be executed later:
ops := new(ui.Ops)
var macro ui.MacroOp
macro.Record()
// Record operations by adding them.
ui.InvalidateOp{}.Add(ops)
...
macro.Stop()
...
// Execute the recorded operations.
macro.Add(ops)
Note that operations added between Record and Stop are not executed until
the macro is Added.
Units
A Value is a value with a Unit attached.