customwidget.go

// Copyright 2010 The Walk Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build windows

package walk

import (
	"unsafe"

	"github.com/lxn/win"
)

const customWidgetWindowClass = `\o/ Walk_CustomWidget_Class \o/`

func init() {
	AppendToWalkInit(func() {
		MustRegisterWindowClass(customWidgetWindowClass)
	})
}

type PaintFunc func(canvas *Canvas, updateBounds Rectangle) error

type PaintMode int

const (
	PaintNormal   PaintMode = iota // erase background before PaintFunc
	PaintNoErase                   // PaintFunc clears background, single buffered
	PaintBuffered                  // PaintFunc clears background, double buffered
)

type CustomWidget struct {
	WidgetBase
	paint               PaintFunc
	invalidatesOnResize bool
	paintMode           PaintMode
}

func NewCustomWidget(parent Container, style uint, paint PaintFunc) (*CustomWidget, error) {
	cw := &CustomWidget{paint: paint}

	if err := InitWidget(
		cw,
		parent,
		customWidgetWindowClass,
		win.WS_VISIBLE|uint32(style),
		0); err != nil {
		return nil, err
	}

	return cw, nil
}

// deprecated, use PaintMode
func (cw *CustomWidget) ClearsBackground() bool {
	return cw.paintMode != PaintNormal
}

// deprecated, use SetPaintMode
func (cw *CustomWidget) SetClearsBackground(value bool) {
	if value != cw.ClearsBackground() {
		if value {
			cw.paintMode = PaintNormal
		} else {
			cw.paintMode = PaintNoErase
		}
	}
}

func (cw *CustomWidget) InvalidatesOnResize() bool {
	return cw.invalidatesOnResize
}

func (cw *CustomWidget) SetInvalidatesOnResize(value bool) {
	cw.invalidatesOnResize = value
}

func (cw *CustomWidget) PaintMode() PaintMode {
	return cw.paintMode
}

func (cw *CustomWidget) SetPaintMode(value PaintMode) {
	cw.paintMode = value
}

func (cw *CustomWidget) WndProc(hwnd win.HWND, msg uint32, wParam, lParam uintptr) uintptr {
	switch msg {
	case win.WM_PAINT:
		if cw.paint == nil {
			newError("paint func is nil")
			break
		}

		var ps win.PAINTSTRUCT

		var hdc win.HDC
		if wParam == 0 {
			hdc = win.BeginPaint(cw.hWnd, &ps)
		} else {
			hdc = win.HDC(wParam)
		}
		if hdc == 0 {
			newError("BeginPaint failed")
			break
		}
		defer func() {
			if wParam == 0 {
				win.EndPaint(cw.hWnd, &ps)
			}
		}()

		canvas, err := newCanvasFromHDC(hdc)
		if err != nil {
			newError("newCanvasFromHDC failed")
			break
		}
		defer canvas.Dispose()

		r := &ps.RcPaint
		bounds := Rectangle{
			int(r.Left),
			int(r.Top),
			int(r.Right - r.Left),
			int(r.Bottom - r.Top),
		}
		if cw.paintMode == PaintBuffered {
			err = cw.bufferedPaint(canvas, bounds)
		} else {
			err = cw.paint(canvas, bounds)
		}

		if err != nil {
			newError("paint failed")
			break
		}

		return 0

	case win.WM_ERASEBKGND:
		if cw.paintMode != PaintNormal {
			return 1
		}

	case win.WM_PRINTCLIENT:
		win.SendMessage(hwnd, win.WM_PAINT, wParam, lParam)

	case win.WM_WINDOWPOSCHANGED:
		wp := (*win.WINDOWPOS)(unsafe.Pointer(lParam))

		if wp.Flags&win.SWP_NOSIZE != 0 {
			break
		}

		if cw.invalidatesOnResize {
			cw.Invalidate()
		}
	}

	return cw.WidgetBase.WndProc(hwnd, msg, wParam, lParam)
}

func (cw *CustomWidget) bufferedPaint(canvas *Canvas, updateBounds Rectangle) error {
	hdc := win.CreateCompatibleDC(canvas.hdc)
	if hdc == 0 {
		return newError("CreateCompatibleDC failed")
	}
	defer win.DeleteDC(hdc)

	buffered := Canvas{hdc: hdc, doNotDispose: true}
	if _, err := buffered.init(); err != nil {
		return err
	}

	w, h := int32(updateBounds.Width), int32(updateBounds.Height)
	if w < 1 {
		w = 1
	}
	if h < 1 {
		h = 1
	}
	hbmp := win.CreateCompatibleBitmap(canvas.hdc, w, h)
	if hbmp == 0 {
		return lastError("CreateCompatibleBitmap failed")
	}
	defer win.DeleteObject(win.HGDIOBJ(hbmp))

	oldbmp := win.SelectObject(buffered.hdc, win.HGDIOBJ(hbmp))
	if oldbmp == 0 {
		return newError("SelectObject failed")
	}
	defer win.SelectObject(buffered.hdc, oldbmp)

	win.SetViewportOrgEx(buffered.hdc, -int32(updateBounds.X), -int32(updateBounds.Y), nil)
	win.SetBrushOrgEx(buffered.hdc, -int32(updateBounds.X), -int32(updateBounds.Y), nil)

	err := cw.paint(&buffered, updateBounds)

	if !win.BitBlt(canvas.hdc,
		int32(updateBounds.X), int32(updateBounds.Y), w, h,
		buffered.hdc,
		int32(updateBounds.X), int32(updateBounds.Y), win.SRCCOPY) {
		return lastError("buffered BitBlt failed")
	}

	return err
}

func (*CustomWidget) CreateLayoutItem(ctx *LayoutContext) LayoutItem {
	return NewGreedyLayoutItem()
}