[PyNewbie08]

Hi,

I am attempting to update the canvas with text and I have a separate class that handles the updates to the text while the main application drives other images that are being added to the canvas. Therefore, I have been passing the Canvas object to the classes that handle modifying the images.

For some reason, this does not work and I believe my issue has to do with understanding how callbacks work. Here's my code below:

class DrawText(CurrentCanvas):
	def __init__(self,CurrentCanvas):
		self.text=0
		self.fillarray={}
		self.resboxoffset=2        
		self.canvas = CurrentCanvas(redraw_callback = self.redraw)
		self.draw=Draw(self.canvas)
		appuifw.app.body=self.canvas
		self.redraw()
		
	def redraw(self):
		self.draw_text()
    	
	def draw_text(self):
		self.clear_text()
		newtext=u"%dlb"%self.text
		self.draw.text((35,105),newtext,(0,192,0),"title")
		
	def clear_text(self):
  		#Rectangle
		self.canvas.rectangle((30,60,90,110), fill=0xFFFFFF) 
		

class DrawImages:
	def drawBaseBackground(self,canvas, image):
		canvas.blit(image, target = (90, 75), scale = 0)
	def drawActionIcon(self,canvas, icon):
		canvas.blit(icon, target = (25, 135), scale = 0)
	def drawAdvantageIcon(self,canvas, icons):
		canvas.blit(icons, target = (60, 205), scale = 0)


canvas=appuifw.Canvas()
appuifw.app.body=canvas

myImages = DrawImages()
e32.ao_sleep(1)
myImages.drawBaseBackground(canvas, base_background)
myImages.drawActionIcon(canvas, icon)
myImages.drawAdvantageIcon(canvas, icons )

carbon = DrawCarbon(canvas)

This results in the error = global name Draw is not defined

However, if I use another canvas in the DrawText class (with no interaction with the other images), the text is written correctly.

Can someone tell me why this may be occurring? Thanks.

[hurenkam]

Originally Posted by PyNewbie08

class DrawText(CurrentCanvas):
	def __init__(self,CurrentCanvas):
		self.text=0
		self.fillarray={}
		self.resboxoffset=2        
		self.canvas = CurrentCanvas(redraw_callback = self.redraw)
		self.draw=Draw(self.canvas)

At this point it seems like you want to instantiate a 'Draw' class, which
is not defined in your code.

Originally Posted by PyNewbie08

This results in the error = global name Draw is not defined

Which is why you get this error.

[PyNewbie08]

I was not able to get this to work correctly. Essentially, what I would like to do is write text over an existing image. Are there any examples of this?

import appuifw
import messaging
import e32
import TopWindow
sample_picture=graphics.Image.open(u"e:\\Images\\sample.png")
canvas.blit(sample_picture, target = (0, 0), scale = 1)
# HOW DO I WRITE TEXT ON TOP OF THE IMAGE?

I tried using the DrawScore class below but this did not work. Is there a simpler way to do this?

[ck.umraliya]

hi PyNewbie08,
I think the error you are getting is due to the undefined function which you are using in the constructor. So once you define it there should be no error.

def __init__(self,CurrentCanvas):
		self.text=0
		self.fillarray={}
		self.resboxoffset=2        
		self.canvas = CurrentCanvas(redraw_callback = self.redraw)
		self.draw=Draw(self.canvas)##error line
		appuifw.app.body=self.canvas
		self.redraw()

[PyNewbie08]

Ahhh, I see.

Is there a reason why the images on the canvas disappear after a few minutes?

[gaba88]

Originally Posted by PyNewbie08

Ahhh, I see.

Is there a reason why the images on the canvas disappear after a few minutes?

hi PyNewbie
does the image automatically disappears aor it disappears on some click event i mean when you press anything.

Hope you got my question

Enjoy Pythoning
Gaba88

[ck.umraliya]

hi PyNewbie08
images on the canvas will dissappear as soon as some click event occurs such as, preseing the menu key and canceling that.
To keep the image fixed on the canvas and overcome the problem explained above you need to use image handle_redraw() method.

[PyNewbie08]

I haven't yet mastered how the canvas works. If any of you have suggestions as to where I can go to get a quick overview, that would be great. I've been working with the example below to prevent the images from disappearing after a few minutes. I get an invalid syntax error on appuifw.app.body=canvas but I believe the error is caused by the handle_redraw code. Could someone explain the problem here and possibly explain how the redraw is supposed to work? Thanks.

import appuifw
import e32
import TopWindow, graphics

from topwindow import *
from appuifw import *
from graphics import *

g_orange = (255,69,0)

canvas=appuifw.Canvas(event_callback=handle_event, redraw_callback=handle_redraw)
appuifw.app.body=canvas
canvas.rectangle([(0,75), (43,220)], g_orange, width=2)  # selected
draw=Draw(canvas)
scoretext=u"Score"
draw.text((0,35),scoretext,g_orange,"title")
canvas.rectangle([(5,95),(100,90)], fill=(g_orange), width=2) 
scoretext=u"0"
draw.text((5,60),scoretext,g_orange,"title")
app_lock = e32.Ao_lock()
app_lock.wait()

[bogdan.galiceanu]

handle_redraw and handle_event are callback functions that you have to define yourself. Here's a working example:

import appuifw
import e32
import TopWindow, graphics

g_orange = (255,69,0)

img=graphics.Image.new((240,320))

img.rectangle([(0,75), (43,220)], g_orange, width=2)  # selected

scoretext=u"Score"

img.text((0,35),scoretext,g_orange,"title")

img.rectangle([(5,95),(100,90)], fill=(g_orange), width=2)

scoretext=u"0"
img.text((5,60),scoretext,g_orange,"title")

def handle_redraw(rect):
	canvas.blit(img)
canvas=appuifw.Canvas(event_callback=None, redraw_callback=handle_redraw)
appuifw.app.body=canvas

app_lock = e32.Ao_lock()
app_lock.wait()

[ck.umraliya]

hi PyNewbie08
To solve the problem related with canvasing you need to understand the concept of image double buffering.
I am soon going to write an article on WiKi over it.

[ck.umraliya]

hi i think bogdan has shown the exact way.
Just to add it i that the concept of first drawing objects on image and then blinking it over the canvas is reffered to Double Buffering Of image-canvas.

[bogdan.galiceanu]

Chintan is right. It is a sort of double buffering. Basically handle_redraw places an image on the canvas. handle_event is a callback for detecting keypresses.

[ck.umraliya]

hi i think bogdan has shown the exact way.
Just to add it i that the concept of first drawing objects on image and then blinking it over the canvas is reffered to Double Buffering Of image-canvas.

[PyNewbie08]

Thanks Bogdan and CK!

Bogdan, this works for the simple rectangle and text image but when I try this on my full prototype, it doesn't work. The only difference between the full prototype and this is that I'm using:

canvas.blit(sample_image, target = (0, 0), scale = 1)

right after the line: appuifw.app.body=canvas

import appuifw
import e32
import TopWindow, graphics

from topwindow import *
from appuifw import *
from graphics import *

g_orange = (255,69,0)

canvas=appuifw.Canvas(event_callback=handle_event, redraw_callback=handle_redraw)
appuifw.app.body=canvas
canvas.rectangle([(0,75), (43,220)], g_orange, width=2)  # selected
draw=Draw(canvas)
scoretext=u"Score"
draw.text((0,35),scoretext,g_orange,"title")
canvas.rectangle([(5,95),(100,90)], fill=(g_orange), width=2) 
scoretext=u"0"
draw.text((5,60),scoretext,g_orange,"title")
app_lock = e32.Ao_lock()
app_lock.wait()

[bogdan.galiceanu]

Can you post the code for the Draw() class? Or, if it's possible, for the full prototype. It would be a lot easier to figure out what is wrong.