Re: How to compute font size ?

On Tue, Jan 1, 2019 at 9:53 AM Nicolas Pinault <[email protected]> wrote:

> GetFullTextExtent() is usefull but not enought.
>

indeed -- there are complications that make it hard to do properly:

Fonts do not, necessarily, scale directly with font size. So text in a 20
pt font is not exactly twice as big as text in a 10 pt font. But it's
pretty close.

I'm not sure I quite understand your use case, but I'd be tempted to get
the font size close by assuming "typical" text -- and then use the actual
text extent to center it.

A little less precise, but easier.

-CHB







> I tried several methods. I ended with the following code :
>
>     def _set_overlay(self, win, text, colour=(192, 192, 192)):
>         dc = wx.ClientDC(win)
>         odc = wx.DCOverlay(self.overlay, dc)
>         odc.Clear()
>         ctx = wx.GraphicsContext.Create(dc)
>         ctx_size = ctx.GetSize()                            # Get window
> size
>         col = wx.Colour(*colour, 128)                       # Add alpha to
> colour
>         brush = ctx.CreateBrush(wx.Brush(wx.Colour((0,0,0,128)))) # Create
> background brush with alpha
>         fnt = wx.Font(wx.FontInfo(10).FaceName("Arial"))    # Create font
> with size 10
>         font = ctx.CreateFont(fnt, col=col)                 # Create
> graphics font
>         ctx.SetFont(font)                                   # Use graphics
> font
>         txt_size = ctx.GetFullTextExtent(text)              # Get text size
>         scale = (ctx_size[0] / 3) / txt_size[0]             # Compute
> scale (text is third the width of the window)
>         fnt.Scale(scale)                                    # Scale
> font
>         font = ctx.CreateFont(fnt, col=col)                 # Create new
> graphics font
>         ctx.SetFont(font)                                   # Use new
> graphicsfont
>         txt_size = ctx.GetFullTextExtent(text)              # Get new text
> size
>         ctx.DrawText(text, (ctx_size[0]-txt_size[0])/2,
> (ctx_size[1]-txt_size[1])/2, brush)   # Draw text (centered)
>         del odc
>
> So : Create a font of size 10, determine the text width with this font
> size, scale the font, and draw with the scaled font.
>
> Nicolas
>
>
>
>
> On Fri, Dec 28, 2018 at 2:40 PM Nicolas Pinault <[email protected]> wrote:
>
>> Hi,
>>
>> In my app, I have a window(a panel) where I write some text as an overlay
>> :
>>
>>      def _set_overlay(self, win, text, colour=(192, 192, 192)):
>>          dc = wx.ClientDC(win)
>>          odc = wx.DCOverlay(self.overlay, dc)
>>          odc.Clear()
>>          ctx = wx.GraphicsContext.Create(dc)
>>          col = wx.Colour(*colour, 128)
>>          brush = ctx.CreateBrush(wx.Brush(wx.Colour((0,0,0,128))))
>>          font = ctx.CreateFont(10, "ARIAL", flags=wx.FONTFLAG_DEFAULT,
>> col=col)
>>          ctx.SetFont(font)
>>          ctx.DrawText(text, 10, 10, brush)
>>          del odc
>>
>> For now, the font size is fixed. I'd like to compute the font size to
>> make the text half the width of the window.
>> What is the best way to compute the font size ?
>>
>> Regards,
>> Nicolas
>>
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>
>
> --
>
> Christopher Barker, Ph.D.
> Oceanographer
>
> Emergency Response Division
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-- 

Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R            (206) 526-6959   voice
7600 Sand Point Way NE   (206) 526-6329   fax
Seattle, WA  98115       (206) 526-6317   main reception

[email protected]

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