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I've been trying to apply matrix transformations to UI objects displaying texts and I ran into some very weird experience. It seems that there are some bugs with the transformations of texts and t_jtextlayout objects. To illustrate the problems, I made two minimal code examples (you can try them by replacing the paint method of the uisimp example). Both will display a "Hello World!" message and a line without transform and then they will draw the same 'painting', but transformed. The transformation in both cases consists of a translation to (40, 40) and a rotation by 60 degrees. The first example uses 

void uisimp_paint ( t_uisimp * x, t_object * patcherview ) {
    const char * text = "Hello World!";
    t_jgraphics *g = ( t_jgraphics * ) patcherview_get_jgraphics ( patcherview );
    t_jfont * font = jfont_create ( "Arial", JGRAPHICS_FONT_SLANT_NORMAL, JGRAPHICS_FONT_WEIGHT_NORMAL, 12.0 );
    t_jmatrix transform;

    // Init variables
    jgraphics_matrix_init ( & transform, 0.5, 0.866, -0.866, 0.5, 40, 40 );

    // Draw stuff before transformation
    jgraphics_move_to ( g, 20, 20 );
    jgraphics_show_text ( g, text );
    jgraphics_line_to ( g, 100, 20 );

    // Apply transformation
    jgraphics_transform ( g, & transform );

    // Draw stuff after transformation
    jgraphics_move_to ( g, 20, 20 );
    jgraphics_show_text ( g, text );
    jgraphics_line_to ( g, 100, 20 );

    // Clean up
    jgraphics_stroke ( g );
    jfont_destroy ( font );

}


If you check the result (text.png), you'll notice that, although the line will be transformed correctly, the text will only rotate correctly; the linear translation is much bigger than expected.

void uisimp_paint ( t_uisimp * x, t_object * patcherview ) {
    const char * text = "Hello World!";
    t_jgraphics *g =  ( t_jgraphics * ) patcherview_get_jgraphics ( patcherview );
    t_jfont * font = jfont_create ( "Arial", JGRAPHICS_FONT_SLANT_NORMAL, JGRAPHICS_FONT_WEIGHT_NORMAL, 12.0 );
    t_jtextlayout * textLayout = jtextlayout_create ( );
    double width, height;
    t_jmatrix transform;

    // Init variables
    jfont_text_measure ( font, text, & width, & height );
    jgraphics_matrix_init ( & transform, 0.5, 0.866, -0.866, 0.5, 40, 40 );

    // Draw stuff before transformation
    jtextlayout_set ( textLayout, text, font, 20, 20, width, height, JGRAPHICS_TEXT_JUSTIFICATION_LEFT, JGRAPHICS_TEXTLAYOUT_NOWRAP );
    jtextlayout_draw ( textLayout, g );
    jgraphics_move_to ( g, 20, 20 );
    jgraphics_line_to ( g, 100, 20 );

    // Apply transformation
    jgraphics_transform ( g, & transform );

    // Draw stuff after transformation
    jtextlayout_set ( textLayout, text, font, 20, 20, width, height, JGRAPHICS_TEXT_JUSTIFICATION_LEFT, JGRAPHICS_TEXTLAYOUT_NOWRAP );
    jtextlayout_draw ( textLayout, g );
    jgraphics_move_to ( g, 20, 20 );
    jgraphics_line_to ( g, 100, 20 );

    // Clean up
    jgraphics_stroke ( g );
    jfont_destroy ( font );
    jtextlayout_destroy ( textLayout );

}


The resulting image (textlayout.png) shows that the line was again transformed correctly, however, the textlayout is completely misplaced and even the rotation is bad.

Is this a bug of the matrix transformations or am I completely misunderstanding something?

I've been trying to apply matrix transformations to UI objects displaying texts and I ran into some very weird experience. It seems that there are some bugs with the transformations of texts and t_jtextlayout objects. To illustrate the problems, I made two minimal code examples (you can try them by replacing the paint method of the uisimp example). Both will display a "Hello World!" message and a line without transform and then they will draw the same 'painting', but transformed. The transformation in both cases consists of a translation to (40, 40) and a rotation by 60 degrees. The first example uses jgraphics_text_show to display the texts:

void uisimp_paint ( t_uisimp * x, t_object * patcherview ) {
	const char * text = "Hello World!";
	t_jgraphics *g = ( t_jgraphics * ) patcherview_get_jgraphics ( patcherview );
	t_jfont * font = jfont_create ( "Arial", JGRAPHICS_FONT_SLANT_NORMAL, JGRAPHICS_FONT_WEIGHT_NORMAL, 12.0 );
	t_jmatrix transform;

	// Init variables
	jgraphics_matrix_init ( & transform, 0.5, 0.866, -0.866, 0.5, 40, 40 );

	// Draw stuff before transformation
	jgraphics_move_to ( g, 20, 20 );
	jgraphics_show_text ( g, text );
	jgraphics_line_to ( g, 100, 20 );

	// Apply transformation
	jgraphics_transform ( g, & transform );

	// Draw stuff after transformation
	jgraphics_move_to ( g, 20, 20 );
	jgraphics_show_text ( g, text );
	jgraphics_line_to ( g, 100, 20 );

	// Clean up
	jgraphics_stroke ( g );
	jfont_destroy ( font );

}


In my other example, I was using a t_jtextlayout object to display the text:

void uisimp_paint ( t_uisimp * x, t_object * patcherview ) {
	const char * text = "Hello World!";
	t_jgraphics *g =  ( t_jgraphics * ) patcherview_get_jgraphics ( patcherview );
	t_jfont * font = jfont_create ( "Arial", JGRAPHICS_FONT_SLANT_NORMAL, JGRAPHICS_FONT_WEIGHT_NORMAL, 12.0 );
	t_jtextlayout * textLayout = jtextlayout_create ( );
	double width, height;
	t_jmatrix transform;

	// Init variables
	jfont_text_measure ( font, text, & width, & height );
	jgraphics_matrix_init ( & transform, 0.5, 0.866, -0.866, 0.5, 40, 40 );

	// Draw stuff before transformation
	jtextlayout_set ( textLayout, text, font, 20, 20, width, height, JGRAPHICS_TEXT_JUSTIFICATION_LEFT, JGRAPHICS_TEXTLAYOUT_NOWRAP );
	jtextlayout_draw ( textLayout, g );
	jgraphics_move_to ( g, 20, 20 );
	jgraphics_line_to ( g, 100, 20 );

	// Apply transformation
	jgraphics_transform ( g, & transform );

	// Draw stuff after transformation
	jtextlayout_set ( textLayout, text, font, 20, 20, width, height, JGRAPHICS_TEXT_JUSTIFICATION_LEFT, JGRAPHICS_TEXTLAYOUT_NOWRAP );
	jtextlayout_draw ( textLayout, g );
	jgraphics_move_to ( g, 20, 20 );
	jgraphics_line_to ( g, 100, 20 );

	// Clean up
	jgraphics_stroke ( g );
	jfont_destroy ( font );
	jtextlayout_destroy ( textLayout );

}


jgraphics-transforms-and-text-display-possibly-a-bug

thanks for trying it out! It's nice to see that this bug is system dependent. I'm on Mac OS X 10.6.8 with Max 5.1.9 and SDK 5.1.7. Is there anybody at Cycling '74 that could give me some advice on how to go on? I'm really stuck with this...

OK, finally I fired an official bug report. Maybe that would help us in getting this solved...

I just tested your code above and it worked fine for me in Max 6 on OSX.

Are you able to test this on your system in both Max 5 and Max 6?

Also you might want to see if it makes a difference if you turn on/off the Native Text Rendering setting in your Max Prefs.

I just tested your code above and it worked fine for me in Max 6 on OSX. 

Are you able to test this on your system in both Max 5 and Max 6? 

Also you might want to see if it makes a difference if you turn on/off the Native Text Rendering setting in your Max Prefs. 

thank you a lot for your answer. I didn't know about the 'Native Text Rendering' setting. Now I turned it off and I can report that I on Max 5 I get the same results than those of Nicholas: the first version will still display the mentioned bug, however, the textlayout version works fine. In Max 6 the bug seems to be gone in both cases, regardless of the value of Native Text Rendering, which is good news, although I need to keep this project Max 5 compatible. Still, it's good to know that disabling native text rendering and using textlayouts helps in Max 5 for this. I guess this would mean that text rendering will require more CPU (as compared to the native rendering), but at least, now I have a solution that I can use.

I wrote about the Native Text Rendering bug a while ago but nobody cared to reply...

https://cycling74.com/forums/bug-with-native-text-rendering

sorry for jumping in a little late.
I wrote about the Native Text Rendering bug a while ago but nobody cared to reply...

JGraphics transforms and text display - possibly a bug (?)