Baffled by CEdit.SetRect and CRect.DeflateRect

Posted on 2002-04-29
Last Modified: 2013-11-20
Baffled by CEdit.SetRect and CRect.DeflateRect

I'm enhancing an MFC dialog app that has overlapping controls. Now I'd like to implement something fancier.  

Here's how it works now ...
mouse over #2 CTreeCtrl control


mouse over #8 CEdit


The glitch is that the left side text in the #8 CEdit isn't visible when the #2 CTreeControl has focus ... it's covered up by the #2 CTreeCtrl.

What I want to implement is having the text in the #8 CEdit window 'auto-fit' when the #2 CTreeCtrl is in the foreground. It would shrink the left margin sufficiently and let auto-wrap keep all the text in view.

I looked over the documentation, and it would seem like CEdit.GetRect + CRect.DeflateRect + CEdit.SetRect would accomplish what I'm looking for.  The vertical scroll bar would be enabled if all the text wouldn't fit into the shrunk CEdit window.

However, I'm getting unexpected behavior. Several of the margins change, instead of just the left.  And the amount of text gets less/truncated. I don't know if I should be normalizing or otherwise doing coordinate transformations ... or if I'm just fouling up.

If you want to tackle this, I've defined a barebones dialog app with the controls and OnToggle defined. It can be downloaded directly at:

It has a member function, OnToggle, that I want to cause the 'margin' of the CEdit to deflate and inflate. The CEdit field is preloaded with a long string with embedded new-lines.  The net result should be the text starting off hidden behind #2 CTreeCtrl, then the toggle deflates the right margin so all the text is visible (and can be seen with the scroll bar), and another toggle inflates the right margin so some of the text is again hidden.

It has the vc6 .dsw, .dsp, and associated files. Note that I'm actually trying to get the #8 Cedit window on the right side, but that would not show up in the 'drawing' above due to proportional fonts.

Question by:l_d_allan

Accepted Solution

Yechezkel earned 100 total points
ID: 6990444
The Problem:

Quote from MSDN on "CEdit::SetRect":
"If the edit control contains a border, the formatting rectangle is reduced by the size of the border. If you adjust the rectangle returned by the GetRect member function, you must remove the size of the border before you pass the rectangle to SetRect."

Each time you call SetRect Windows shrinks the formatting rectangle by the size of the edit control border, so the formatting rectangle keeps getting smaller.

The Solution:

Quote from MSDN on "Changing the Formatting Rectangle":
"The visibility of an edit control's text is governed by the dimensions of its window rectangle and its formatting rectangle. The window rectangle is the client area of the window containing the edit control. The formatting rectangle is a construct maintained by the system for formatting the text displayed in the window rectangle. When an edit control is first displayed, the two rectangles are identical on the screen."

By default the formatting rectangle is set to the same as the client area of the edit control. So instead of getting the formatting rectangle and adjusting that, get the client rectangle (using GetClientRect), adjust it, and pass that to CEdit::SetRect.

Author Comment

ID: 7000396
Worked very well.  Thanks.

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