[plt-scheme] GUI guides?

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Mon Jul 6 08:03:16 EDT 2009

That's a fine way to sizing the window, but if you want to print the
window, that sizing information will be wrong.

Generally, you want to abstract over the dc for all drawing (maybe
you've done that already) and then just pass in the appropriate that
you get from the system (usually from the get-dc method of a canvas%,
the on-paint method of editor<%> or the print method of an editor<%>).
Just be careful you don't use a global values that are computed from
the wrong dc.


On Mon, Jul 6, 2009 at 6:55 AM, Hugh Myers<hsmyers at gmail.com> wrote:
> Good point. Are you saying this is the wrong approach to correctly
> sizing a window displaying a chess font? If so what would you
> recommend?
> --hsm
> On Sun, Jul 5, 2009 at 10:00 PM, Hugh Myers<hsmyers at gmail.com> wrote:
>> The key to width of text is:
>>> (define dc (send c get-dc))
>>> (send dc get-text-extent "123456787" (make-object font% 24 "Chess Adventurer" 'symbol))
>> 264.0
>> 32.0
>> 0.0
>> 0.0
>> This while the dc in question exists...
>> --hsm
>> On Sun, Jul 5, 2009 at 9:12 PM, Hugh Myers<hsmyers at gmail.com> wrote:
>>> Added to list:
>>> Care and feeding of Status Line---a subject worth a guide in of itself:
>>> Create a status line
>>> Open a status line
>>> Write to a status line
>>> Close a status line
>>> Remove a status line
>>> Note that the overall status line is partitioned into writable areas.
>>> For instance for a chess board, I would want to show the move text,
>>> the move number and the move ply (move number without regard to color;
>>> ply 1 is move 1 as is ply 2 [white's move followed by black's move
>>> etc.]). Perhaps also information on castling, draw information etc. An
>>> example rich environment.
>>> --hsm
>>> On Sun, Jul 5, 2009 at 8:41 PM, Hugh Myers<hsmyers at gmail.com> wrote:
>>>> Thanks for the pointer to dc% What you mention seems like a logical
>>>> (heaven forbid) arrangement given the concepts involved. Having
>>>> survived the age of roll-your-own gui (usually text), original
>>>> windows, and then MFC this should be just another notch in my
>>>> gui-belt. Even as we e-speak I'm in the middle of investigating frame%
>>>> which has some of the answers in my shopping-list. I think one of the
>>>> things that will be in my version of 'GUI Editor Guide' will be a list
>>>> of what all can be set/modified for a given window. Sometimes it is
>>>> easier to pick and choose from such a list than to comb a detailed
>>>> reference--- I think as a guide, this approach might be the one to go
>>>> with.
>>>> --hsm
>>>> On Sun, Jul 5, 2009 at 6:51 PM, Ryan Culpepper<ryanc at ccs.neu.edu> wrote:
>>>>> Hugh Myers wrote:
>>>>>> Am solving some of these as I try and think of questions to ask. Some
>>>>>> of the answers raise questions about what is or isn't do-able. For
>>>>>> instance given fixed width symbol font (like all chess fonts) it would
>>>>>> be nice to ask how wide and how tall a given text string is. This
>>>>>> could be used to 'size' the window before display. Nothing I've seen
>>>>>> yet even hints that this is possible, yet it seems quit reasonable.
>>>>> I think you want 'get-text-extent' in 'dc<%>' (drawing context).
>>>>> Here are some rough guidelines:
>>>>>  - 'editor<%>' and 'text%' deal with the text, its styles, modifications to
>>>>> the text, high-level display concerns (word wrapping, visible/ region, etc).
>>>>>  - 'canvas<%>' and 'editor-canvas%' deal with the gui concerns: dimensions
>>>>> of the editor widget, its auxiliary gui elements (scrollbars), etc.
>>>>>  - 'dc<%>' deals with rendering issues, like how big a string in a
>>>>> particular font will be rendered on screen.
>>>>> Browsing those classes and interfaces is a good way to get an idea of what
>>>>> functionality is available and how it's provided. Remember to look at the
>>>>> superclasses and superinterfaces, too.
>>>>> Ryan
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