Kivy: Interactive Applications in Python by 未知

Author:未知
Language: eng
Format: epub
Publisher: Packt Publishing

The structure in line94 to 100 is already familiar. Line 96 makes sure that the ToolButton is in the 'down' state and that the event happened in the DrawingSpace instance (referenced by ds). Remember that the parent of the ToolButton is ToolBox, and that we added an attribute that references the DrawingSpace instance in comiccreator.kv at the beginning of the chapter.

The draw method is called in line 98 and it will draw the respective shapes according to the derived classes (ToolStickMan, ToolCircle, and ToolLine). We need to be sure that we send the right coordinates to the draw method. Therefore, before calling on it we need to translate the absolute coordinates of the event to relative coordinates with the to_widget event (line 97). We know that the coordinates we received (touch.x and touch.y) are absolute because ToolStickman is not a RelativeLayout, whereas the DrawingSpace (ds) is.

Let's continue studying the toolbox.py file and see how ToolStickMan actually adds the StickMan instances:

104. class ToolStickman(ToolButton): 105. def draw(self, ds, x, y): 106. sm = StickMan(width=48, height=48) 107. sm.center = (x,y) 108. ds.add_widget(sm)

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