我正在尝试学习如何使用图表库和Cairo/GTK后端绘制图表。我要显示一个空白窗口,但我的绘图无法渲染。我做错了什么?
module Main where
import Control.Monad.Trans (liftIO)
import Graphics.UI.Gtk
import Diagrams.Backend.Cairo
import Diagrams.Backend.Cairo.Gtk
import Diagrams.Prelude
main :: IO ()
main = do
initGUI
window <- windowNew
canvas <- drawingAreaNew
canvas `on` sizeRequest $ return (Requisition 1000 1000)
set window [ containerBorderWidth := 10,
containerChild := canvas ]
canvas `on` exposeEvent $ renderFigure
onDestroy window mainQuit
widgetShowAll window
mainGUI
renderFigure :: EventM EExpose Bool
renderFigure = do
win <- eventWindow
liftIO $ renderToGtk win $ toGtkCoords figure
-- liftIO $ defaultRender win figure
return True
figure :: Diagram Cairo R2
figure = unitCircle # scaleX 0.5 # rotateBy (1/6) # scale 50
我尝试使用"defaultRender"(如上所述),但这给出了一个类型错误:显然"win"不是正确的类型。
我已经阅读了图表的教程和用户手册,但它实际上并没有告诉您如何使用Cairo后端。
更新:我有要渲染的椭圆。 "renderFigure"函数现在说:
renderFigure :: DrawingArea -> EventM EExpose Bool
renderFigure canvas = do
-- win <- eventWindow
liftIO $ do
-- diagramArea <- widgetGetDrawWindow canvas
-- renderToGtk diagramArea $ toGtkCoords figure
defaultRender canvas figure
return True
传入的绘图区域是"画布on
exposeEvent..."中引用的"画布"设置。
但是我仍然无法让它使用"renderToGtk"渲染固定大小的图表。
更新2:感谢Joachim Breitner的回答,我现在得到了最小的GTK程序,看起来像这样,准备好了你的剪切和粘贴乐趣。
module Main where
import Control.Monad.Trans (liftIO)
import Graphics.UI.Gtk
import Diagrams.Backend.Cairo
import Diagrams.Backend.Cairo.Gtk
import Diagrams.Prelude
main :: IO ()
main = do
initGUI
window <- windowNew
canvas <- drawingAreaNew
canvas `on` sizeRequest $ return (Requisition 256 256)
set window [ containerBorderWidth := 10,
containerChild := canvas ]
canvas `on` exposeEvent $ renderFigure
onDestroy window mainQuit
widgetShowAll window
mainGUI
renderFigure :: EventM EExpose Bool
renderFigure = do
win <- eventWindow
liftIO $ renderToGtk win $ toGtkCoords figure
return True
figure :: Diagram Cairo R2
figure = unitCircle # scaleX 0.5 # rotateBy (1/6) # scale 50 # fc red
您的初始代码实际上有效。但是 renderToGtk 不会缩放图像,因此它看起来相当小,太小而无法在该行宽下看到。但是尝试
figure :: Diagram Cairo R2
figure = unitCircle # scaleX 0.5 # rotateBy (1/6) # scale 50 # fc red
它会像魅力一样工作!
您可以注意到,在最新版本的图表中,您应该使用
import Diagrams.Backend.Gtk
而不是
import Diagrams.Backend.Cairo.Gtk
和
figure :: Diagram Cairo
而不是
figure :: Diagram Cairo R2
结果现在如下所示:
module Main where
import Control.Monad.Trans (liftIO)
import Graphics.UI.Gtk
import Diagrams.Backend.Cairo
import Diagrams.Backend.Gtk
import Diagrams.Prelude
main :: IO ()
main = do
initGUI
window <- windowNew
canvas <- drawingAreaNew
canvas `on` sizeRequest $ return (Requisition 256 256)
Graphics.UI.Gtk.set window [ containerBorderWidth := 10,
containerChild := canvas ]
canvas `on` exposeEvent $ renderFigure
onDestroy window mainQuit
widgetShowAll window
mainGUI
renderFigure :: EventM EExpose Bool
renderFigure = do
win <- eventWindow
liftIO $ renderToGtk win $ toGtkCoords figure
return True
figure :: Diagram Cairo
figure = unitCircle # scaleX 0.5 # rotateBy (1/6) # scale 50 # fc red