TRect and TextRect Question
lazarus / 39-Graphics

----------------------------------------------------------------------
Dan3468298 · 2020-07-28 00:13

When defining a TRect you use cartesian plane coordinates.  But when
using TextRect, it ignores TRect Top and left and uses 0 value.  My
guess is this is so for when TRect is used on cartesian plane with
minus values for graphing.   I am trying to understand the
motivations.  Thanks for any input.

----------------------------------------------------------------------
wp · 2020-08-01 15:58

I don't know what you are talking about. The TextRect method of the
canvas?

In this case, the usage of the coordinates depends on the settings for
Layout and Alignment in the canvas' TextStyle. Please play with the
attached code - I wrote it on Windows but it should work also on Mac.

The rectangle Rect passed to Canvas.TextRect(Rect, x, y, Text,
TextStyle) defines the box within which the text is written.
x is used only when TextStyle.Alignment is taLeftJustify, and y is
used only when TextStyle.Layout is tlTop. Their origin is the origin
of the canvas on which painting occurs. This means that when you want
to paint in the top/left corner of the specified Rect you must set x =
Rect.Left and y = Rect.Top. So, if you set x=0 and y=0 and have
Rect.Left > 0 and Rect.Top > 0 there is probably no output because of
clipping (which can be turned off by setting TextRect.Clipping :=
false).

If you want to paint the text centered at the top of the Rect use
TextStyle.Alignment := taCenter, TextStyle.Layout := tlTop, x will be
ignored.

If you want to right-align the text within the Rect use
TextStyle.Alignment := taRightJustify, TextStyle.Layout := tlTop. x
will be ignored.

If you want to right-align the text within the Rect but move it 20
pixels below the top edge use the same TextStyle settings but set y :=
Rect.Top + 20;

If you want to paint the text centered both vertically and
horizontally within Rect use TextStyle.Alignment := taCenter and
TextStyle.Layout.tlCenter, both x and y will be ignored. Etc...

Note that TTextStyle is a record which does not have setter
procedures; therefore you can assign only a complete record to
Canvas.TextStyle. You must use an intermediate variable to change
record elements. Do not forget to initialize this record with the
current TextStyle settings:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var  ts:
TTextStyle;begin  ts := Canvas.TextStyle;  ts.Alignment := taCenter; 
ts.Layout := tlCenter;  Canvas.TextRect(Rect(10, 10, 490, 390), 0, 0,
'My text', ts); The temporary TextStyle variable can be omitted in the
latter call, but then the temp variable must be re-assigned to
canvas.TextStyle:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var  ts:
TTextStyle;begin  ts := Canvas.TextStyle;  ts.Alignment := taCenter; 
ts.Layout := tlCenter;  Canvas.TextStyle := ts; 
Canvas.TextRect(Rect(10, 10, 490, 390), 0, 0, 'My text');

----------------------------------------------------------------------
circular · 2020-08-02 08:26

The (x,y) coordinates are redundant in most cases. TextRect could
simply use (Left,Top) of rectangle.

Though I can see a case where it makes sense. If you enable clipping
and disable word wrap, you can draw some text at location (x,y) and
clip it according to any rectangle.

----------------------------------------------------------------------
Dan3468298 · 2020-08-02 17:53

Yes, using TextOut on a Canvas.  Sorry for forgetting those details.

----------------------------------------------------------------------
asmx · 2024-01-21 04:52

I use TextExtent to measure the width and height of a single line of
text, reduce its width and then pass it into TextRect. The printing
effect is that the text is wrapped. But I cannot get the actual height
occupied by the printed text. Is there a good way to get it?

Quote from: wp on August 01, 2020, 05:58:03 pmI don't know what you
are talking about. The TextRect method of the canvas?

In this case, the usage of the coordinates depends on the settings for
Layout and Alignment in the canvas' TextStyle. Please play with the
attached code - I wrote it on Windows but it should work also on Mac.

The rectangle Rect passed to Canvas.TextRect(Rect, x, y, Text,
TextStyle) defines the box within which the text is written.
x is used only when TextStyle.Alignment is taLeftJustify, and y is
used only when TextStyle.Layout is tlTop. Their origin is the origin
of the canvas on which painting occurs. This means that when you want
to paint in the top/left corner of the specified Rect you must set x =
Rect.Left and y = Rect.Top. So, if you set x=0 and y=0 and have
Rect.Left > 0 and Rect.Top > 0 there is probably no output because of
clipping (which can be turned off by setting TextRect.Clipping :=
false).

If you want to paint the text centered at the top of the Rect use
TextStyle.Alignment := taCenter, TextStyle.Layout := tlTop, x will be
ignored.

If you want to right-align the text within the Rect use
TextStyle.Alignment := taRightJustify, TextStyle.Layout := tlTop. x
will be ignored.

If you want to right-align the text within the Rect but move it 20
pixels below the top edge use the same TextStyle settings but set y :=
Rect.Top + 20;

If you want to paint the text centered both vertically and
horizontally within Rect use TextStyle.Alignment := taCenter and
TextStyle.Layout.tlCenter, both x and y will be ignored. Etc...

Note that TTextStyle is a record which does not have setter
procedures; therefore you can assign only a complete record to
Canvas.TextStyle. You must use an intermediate variable to change
record elements. Do not forget to initialize this record with the
current TextStyle settings:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var  ts:
TTextStyle;begin  ts := Canvas.TextStyle;  ts.Alignment := taCenter; 
ts.Layout := tlCenter;  Canvas.TextRect(Rect(10, 10, 490, 390), 0, 0,
'My text', ts); The temporary TextStyle variable can be omitted in the
latter call, but then the temp variable must be re-assigned to
canvas.TextStyle:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i var  ts:
TTextStyle;begin  ts := Canvas.TextStyle;  ts.Alignment := taCenter; 
ts.Layout := tlCenter;  Canvas.TextStyle := ts; 
Canvas.TextRect(Rect(10, 10, 490, 390), 0, 0, 'My text');

----------------------------------------------------------------------
circular · 2024-01-21 06:08

@asmx

After investigating a bit, the best thing I found is to call LCLIntf
directly.

Here is a function that you will do that for you:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses
LCLIntf, LCLType, Types; function TextExtent(ACanvas: TCanvas; const
AText: string; AMaxWidth: Integer; const AStyle: TTextStyle):
TSize;var bounds: TRect;  flags: Cardinal;begin  bounds := Rect(0, 0,
AMaxWidth, MaxInt);  flags := DT_CALCRECT;  if AStyle.SingleLine then
flags := flags OR DT_SINGLELINE;  if AStyle.EndEllipsis then flags :=
flags or DT_END_ELLIPSIS;  if AStyle.ExpandTabs then flags := flags OR
DT_EXPANDTABS;  if AStyle.Wordbreak then flags := flags OR
DT_WORDBREAK;  if AStyle.RightToLeft then flags := flags or
DT_RTLREADING;  if not AStyle.ShowPrefix then flags := flags OR
DT_NOPREFIX;  LCLIntf.DrawText(ACanvas.Handle, PChar(AText),
Length(AText), bounds, flags);  Result := Size(bounds.Width,
bounds.Height);end; 
I suppose this function could be added to TCanvas.

----------------------------------------------------------------------
asmx · 2024-01-21 08:18

@circular

Thank you for reply. I'm using Printer4Lazarus in my code and
LCLIntf.DrawText seem can't to draw content onto the
Printer.Canvas.Handle.

Quote from: circular on January 21, 2024, 07:08:33 am@asmx

After investigating a bit, the best thing I found is to call LCLIntf
directly.

Here is a function that you will do that for you:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i uses
LCLIntf, LCLType, Types; function TextExtent(ACanvas: TCanvas; const
AText: string; AMaxWidth: Integer; const AStyle: TTextStyle):
TSize;var bounds: TRect;  flags: Cardinal;begin  bounds := Rect(0, 0,
AMaxWidth, MaxInt);  flags := DT_CALCRECT;  if AStyle.SingleLine then
flags := flags OR DT_SINGLELINE;  if AStyle.EndEllipsis then flags :=
flags or DT_END_ELLIPSIS;  if AStyle.ExpandTabs then flags := flags OR
DT_EXPANDTABS;  if AStyle.Wordbreak then flags := flags OR
DT_WORDBREAK;  if AStyle.RightToLeft then flags := flags or
DT_RTLREADING;  if not AStyle.ShowPrefix then flags := flags OR
DT_NOPREFIX;  LCLIntf.DrawText(ACanvas.Handle, PChar(AText),
Length(AText), bounds, flags);  Result := Size(bounds.Width,
bounds.Height);end; 
I suppose this function could be added to TCanvas.

----------------------------------------------------------------------
wp · 2024-01-21 09:54

Quote from: asmx on January 21, 2024, 09:18:17 amThank you for reply.
I'm using Printer4Lazarus in my code and LCLIntf.DrawText seem can't
to draw content onto the Printer.Canvas.Handle.
What is happening? It should work - see attachment. Sometimes
(strange, not always...) the unit OSPrinters must be included in the
uses clause.

----------------------------------------------------------------------
asmx · 2024-01-21 12:04

My project type is library. I also uses Interfaces, Classes, SysUtils,
Graphics, LCLIntf, LCLType, Types, Printers, osprinters, etc...

Print result is nothing printed(bounds is Rect(0,0,
Printer.PaperSize.Width, Printer.PaperSize.Height) and flags is
DT_CALCRECT or DT_EXPANDTABS or DT_WORDBREAK or DT_NOPREFIX).

----------------------------------------------------------------------
circular · 2024-01-21 16:04

Quote from: asmx on January 21, 2024, 09:18:17 am@circular

Thank you for reply. I'm using Printer4Lazarus in my code and
LCLIntf.DrawText seem can't to draw content onto the
Printer.Canvas.Handle.
Hi @asmx,

That would be a different issue. The function I've provided is not
designed to draw but to measure the text.

When you draw text, you can use Canvas.TextRect. This doesn't work for
you?

Otherwise you could adapt the procedure I've provided by removing the
DT_CALCRECT flag. If you do so, don't forget to provide coordinates
(when measuring it is assumed to be at the origin 0,0).

Regards

----------------------------------------------------------------------
wp · 2024-01-21 17:16

Quote from: asmx on January 21, 2024, 01:04:40 pmPrint result is
nothing printed(bounds is Rect(0,0, Printer.PaperSize.Width,
Printer.PaperSize.Height) and flags is DT_CALCRECT or DT_EXPANDTABS or
DT_WORDBREAK or DT_NOPREFIX).
circular is right: DrawText has two purposes, depending on whether the
flag DT_CALCRECT is included or not. When it is included in the flags
passed to the DrawText function, then nothing is drawn, only the size
of the rectangle is measured and returned in the rect parameter (where
the width of the rect is not changed, only the height). So, if you
want to draw, you must remove the DT_CALCRECT flag. See the code in my
previous project:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i     //
Define the rectangle into which the print will go. Height can be 0,
will be adjust so that the text fits in.    R := Rect(...);       //
Set the flags, here only workbreak.    flags := DT_WORDBREAK;       //
1st call to DrawText for measuring (with DT_CALCRECT). Afterwards the
height of R has been adjusted.    DrawText(Printer.Canvas.Handle,
PChar(PRINT_TEXT), Length(PRINT_TEXT), R, flags or DT_CALCRECT);     
// 2nd call to DrawRect, now without DT_CALCRECT to draw wrapped text
inside R.     DrawText(Printer.Canvas.Handle, PChar(PRINT_TEXT),
Length(PRINT_TEXT), R, flags);       // to verify that R is correct:
draw rectangle around the text, same rectangle size as used for text
drawing.    Printer.Canvas.Rectangle(R);

----------------------------------------------------------------------
asmx · 2024-01-22 12:26

@wp @circular

Thanks for reply again

This solved my problem, but I found a new problem, the alignment
properties don't seem to take effect (DT_LEFT, DT_CENTER, DT_RIGHT),
but I found a workaround where I manually reset the Right value after
measuring the bounds before actually Print them.

----------------------------------------------------------------------
wp · 2024-01-22 15:35

Quote from: asmx on January 22, 2024, 01:26:55 pmthe alignment
properties don't seem to take effect (DT_LEFT, DT_CENTER, DT_RIGHT),
but I found a workaround where I manually reset the Right value after
measuring the bounds before actually Print them.
For measuring? The alignment should not play a role here, the only
thing which counts is the width of the longest line and the number of
lines (after wrapping).
For drawing? I don't understand then - it works here, see attached
modification of the previously sent project.

----------------------------------------------------------------------
circular · 2024-01-22 16:39

@asmx Glad to hear it works for you now.

----------------------------------------------------------------------
asmx · 2024-01-24 15:16

Quote from: wp on January 22, 2024, 04:35:24 pmQuote from: asmx on
January 22, 2024, 01:26:55 pmthe alignment properties don't seem to
take effect (DT_LEFT, DT_CENTER, DT_RIGHT), but I found a workaround
where I manually reset the Right value after measuring the bounds
before actually Print them.
For measuring? The alignment should not play a role here, the only
thing which counts is the width of the longest line and the number of
lines (after wrapping).
For drawing? I don't understand then - it works here, see attached
modification of the previously sent project.

@wp
Sorry, My English skills are not good enough, Some aspects may not be
described clearly enough, and Thanks again  There are currently no
other issues.

I found the problem, when the text to be printed is short and not long
enough to wrap, it cannot be aligned properly.