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The Border Spacing Flags for Padding Controls

We've seen the Alignment flags, so now we'll look into the Border Spacing flags. These flags have almost nothing to do with the Alignment flags, yet they must be logically "OR"ed into the value of the flag= argument along with any Alignment flags that are needed. These flags are used to specify which sides of the control that are to be bordered (padded) with a space the size of the value of the border= argument. Any combination of these flags may be used in the flag= argument, but they will all be assigned the single border= value of space (in pixel units).

Border Spacing Flag Constants:

• wx.TOP

• wx.BOTTOM

• wx.LEFT

• wx.RIGHT

• wx.ALL

The wx.ALL flag is a convenience definition that specifies that all four sides of the control are to be bordered.

Here's the current state of the sample program:

I want to put a small separation between the StaticText and the TextCtrl. We've seen how to put in a square space with the .AddSpacer() method and to .Add() a rectangular space. Here's yet another way using the flag= and border= parameters. We could either border the top of the TextCtrl or the bottom of the StaticText or even border both. I hope you now see why just adding a spacer in between the controls is simpler. For now, the top of the TextCtrl will be padded. All that's needed to be done is to modify the .Add() statement for the TextCtrl to put in, say, 7 pixels of border padding.

It was :

        allCtrls_vertSizer.Add( self.myListing_txtCtrl, flag=wx.ALIGN_CENTER )

Change it to:

        allCtrls_vertSizer.Add( self.myListing_txtCtrl, flag=wx.ALIGN_CENTER | wx.TOP, border=7 )

Note that the effect of wx.ALIGN_CENTER has absolutely nothing at all to do with the effect of wx.TOP other than they are both applied to the same control. We now get:

The appearance is now a little nicer and it was easy to do. But, it is more direct and clearer to simply insert the line:

allCtrls_vertSizer.Add( (0, 7) )            # A one-dimensional vertical spacer. The best option, overall.

or even:

allCtrls_vertSizer.AddSpacer( 7 )       # A square spacer. It's minor axis dimension wont't interfere in this case.

When it comes to spacers, "there's more than one way to skin a cat". However, another person who is tries to figure out your code using the wx.TOP argument has to make the effort to realize that the wx.ALIGN_CENTER parameter has nothing to do with the wx.TOP parameter even though they are lumped together in the same flag= argument.

The border padding flags can get very confusing to use and modify, especially if adjacent controls both use them. It's far simpler and easier to write and understand your code by just inserting a spacer using a separate statement. Doing this completely isolates the effect of the space and applies it to exactly where it is needed without any unintentional side effects to any other sdjacent controls. In this regard it is better to use either of the .Add( (w, 0) ) or .Add( (0, h) ) spacer insertion statements rather than the .AddSpacer( n ) statement. A square spacer's minor axis dimension unintentionally interfere with other adjacent controls or sizer. Using either of the one-dimensional spacers guarantees this can not happen. But, the dimension value must be placed in the proper ordinate position of the given (x, y) coordinate.

Having not to even to think about which is the major and minor axes of a BoxSizer can be totally avoided by using this simple function:

   1 def AddLinearSpacer( boxsizer, pixelSpacing ) :
   2     """ A one-dimensional spacer along only the major axis for any BoxSizer """
   3 
   4     orientation = boxsizer.GetOrientation()
   5     if   (orientation == wx.HORIZONTAL) :
   6         boxsizer.Add( (pixelSpacing, 0) )
   7 
   8     elif (orientation == wx.VERTICAL) :
   9         boxsizer.Add( (0, pixelSpacing) )
  10     #end if
  11 
  12 #end def

This algorithm is so simple that it's incomprehensible to me why this hasn't already been built into the wx.BoxSizer as a method. I guess this is just another example of the BoxSizer's "Design by Committee". Using this function is easier and foolproof, axes-wise. E.g.:

   1 AddLinearSpacer( allCtrls_vertSizer, 7 )        # This method determines the sizer's orientation by itself.

AddLinearSpacer.py

That's all there is to spacing controls from each other and from the edges of the page. We'll now see how the BoxSizer can automatically resize a control when the page is resized.