如何将图库与GTK drawables一起使用？

Question

我正在尝试学习如何使用图表库和Cairo/GTK后端绘制图表.我有一个空白的窗口出现,但我的绘图不会呈现.我究竟做错了什么？

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

我尝试过使用"defaultRender"(如上所述),但这会产生类型错误: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你如何使用Cairo后端.

更新:我有椭圆渲染."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DrawingArea是"canvas onexposeEvent ..."设置中引用的"canvas ".

但我仍然无法使用"renderToGtk"渲染固定大小的图表.

更新2:感谢Joachim Breitner的回答,我现在已经有了这样的最小GTK图表程序,为您的剪切和粘贴乐趣做好准备.

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  

Answer 1

您的初始代码确实有效.但renderToGtk不会缩放图像,因此它看起来相当小,太小而无法在该线宽处看到.但试试吧

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!