112 lines
3.8 KiB
Go
112 lines
3.8 KiB
Go
// 16 december 2015
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package ui
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import (
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"unsafe"
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)
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// #include "pkgui.h"
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import "C"
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// Area is a Control that represents a blank canvas that a program
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// can draw on as it wishes. Areas also receive keyboard and mouse
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// events, and programs can react to those as they see fit. Drawing
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// and event handling are handled through an instance of a type
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// that implements AreaHandler that every Area has; see AreaHandler
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// for details.
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//
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// There are two types of areas. Non-scrolling areas are rectangular
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// and have no scrollbars. Programs can draw on and get mouse
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// events from any point in the Area, and the size of the Area is
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// decided by package ui itself, according to the layout of controls
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// in the Window the Area is located in and the size of said Window.
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// There is no way to query the Area's size or be notified when its
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// size changes; instead, you are given the area size as part of the
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// draw and mouse event handlers, for use solely within those
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// handlers.
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//
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// Scrolling areas have horziontal and vertical scrollbars. The amount
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// that can be scrolled is determined by the area's size, which is
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// decided by the programmer (both when creating the Area and by
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// a call to SetSize). Only a portion of the Area is visible at any time;
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// drawing and mouse events are automatically adjusted to match
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// what portion is visible, so you do not have to worry about scrolling
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// in your event handlers. AreaHandler has more information.
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//
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// The internal coordinate system of an Area is points, which are
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// floating-point and device-independent. For more details, see
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// AreaHandler. The size of a scrolling Area must be an exact integer
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// number of points (that is, you cannot have an Area that is 32.5
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// points tall) and thus the parameters to NewScrollingArea and
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// SetSize are ints. All other instances of points in parameters and
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// structures (including sizes of drawn objects) are float64s.
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type Area struct {
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ControlBase
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a *C.uiArea
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ah *C.uiAreaHandler
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scrolling bool
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}
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// NewArea creates a new non-scrolling Area.
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func NewArea(handler AreaHandler) *Area {
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a := new(Area)
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a.scrolling = false
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a.ah = registerAreaHandler(handler)
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a.a = C.uiNewArea(a.ah)
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a.ControlBase = NewControlBase(a, uintptr(unsafe.Pointer(a.a)))
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return a
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}
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// NewScrollingArea creates a new scrolling Area of the given size,
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// in points.
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func NewScrollingArea(handler AreaHandler, width int, height int) *Area {
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a := new(Area)
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a.scrolling = true
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a.ah = registerAreaHandler(handler)
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a.a = C.uiNewScrollingArea(a.ah, C.int(width), C.int(height))
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a.ControlBase = NewControlBase(a, uintptr(unsafe.Pointer(a.a)))
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return a
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}
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// Destroy destroys the Area.
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func (a *Area) Destroy() {
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unregisterAreaHandler(a.ah)
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a.ControlBase.Destroy()
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}
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// SetSize sets the size of a scrolling Area to the given size, in points.
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// SetSize panics if called on a non-scrolling Area.
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func (a *Area) SetSize(width int, height int) {
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if !a.scrolling {
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panic("attempt to call SetSize on non-scrolling Area")
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}
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C.uiAreaSetSize(a.a, C.int(width), C.int(height))
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}
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// QueueRedrawAll queues the entire Area for redraw.
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// The Area is not redrawn before this function returns; it is
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// redrawn when next possible.
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func (a *Area) QueueRedrawAll() {
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C.uiAreaQueueRedrawAll(a.a)
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}
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// ScrollTo scrolls the Area to show the given rectangle; what this
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// means is implementation-defined, but you can safely assume
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// that as much of the given rectangle as possible will be visible
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// after this call. (TODO verify this on OS X) ScrollTo panics if called
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// on a non-scrolling Area.
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func (a *Area) ScrollTo(x float64, y float64, width float64, height float64) {
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if !a.scrolling {
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panic("attempt to call ScrollTo on non-scrolling Area")
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}
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C.uiAreaScrollTo(a.a, C.double(x), C.double(y), C.double(width), C.double(height))
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}
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// TODO BeginUserWindowMove
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// TODO BeginUserWindowResize
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