Am 23.10.2013 17:50, schrieb ListMember:
On 2013-10-23 18:10, Sven Barth wrote:
Am 23.10.2013 17:06, schrieb Sven Barth:
Am 23.10.2013 08:59, schrieb ListMember:
Hello,
I am trying to find where WriteLn is declared; but, apparently,
WriteLn is among the select few that Lazarus will ignore 'Find
Declaration' requests --at least that's how it behaves (latest
Lazarus stable) on my side.
My ultimate goal, after finding where it is declared, is to locally
modify that part of the sources so that (instead of writing to the
console) it will use a global callback to display whatever
WriteLn'ed in a TMemo.
Write(Ln), Read(Ln), WriteStr and ReadStr are compiler magic
functions which are not available in Pascal source.
Or, is there already an alternative to redirect console output to
the running GUI?
The Pascal IO mechanism relies on variables of type "file" or of
type "text". For the latter you can specify your own "textdriver"
with which you can replace the e.g. "Output" variable (which is used
by "Write(Ln)" without a file argument) which can then redirect the
output to something else. For an example of how to implement a text
driver you can take a look at the "StreamIO" (
http://www.freepascal.org/docs-html/fcl/streamio/index.html ) unit
provided with Free Pascal (in
$fpcdir/packages/fcl-base/src/streamio.pp). There a text driver is
implemented which allows to "assign" streams to TextFile variables
and thus to use Write(Ln)/Read(Ln) on them. You'll need to implement
something similar for e.g. a memo (or whatever method you want to
use to display the output).
And I just found an example which already does this for TCustomEdit
descendants: http://kd5col.info/swag/DELPHI/0017.PAS.html
I've not tested it in FPC, so maybe small adjustments might be
necessary...
Wow.
This is far too (incredibly) elaborate.
It's a bit like giving me plans to set up an army to invade a country
when all I want to do is to visit it as a tourist :)
No, this is the officially supported way to interfere with Pascal's IO
system.
As I mentioned in my first post, I am prepared to alter the compiler
sources; and I had this in mind:
I would like to add these to a common unit --such as globals.pas
What would adding a callback to "globals.pas" provide? The string that
is written by Writeln is created at runtime and not at compile time.
type
TMyWriteLnCallback = procedure(AText: String);
var
GMyWriteLnCallback: TMyCallback = nil;
and then, wherever the 'compiler magic' for WriteLn is, use something
like
if Assigned(GMyWriteLnCallback) then GMyWriteLnCallback(TextStuff)
else {do the usual console output}
So, could someone tell me where I have to inject these lines.
I've already written you how you can do it. Write a text driver which
uses your callback function.
This is much easier than trying to understand how the compiler handles
Writeln plus you don't need to manipulate the compiler or the RTL for that.
Regards,
Sven
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