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STR #3064

Trouble Report Files:

	Name/Time/Date	Filename/Size
	#1  greg.ercolano 12:04 Mar 09, 2014	patch.txt 4k

Trouble Report Comments:

	Name/Time/Date	Text
	#1  greg.ercolano 12:03 Mar 09, 2014	Reporting this on behalf of Gonzalo. This may affect 1.3 as well, which is why I'm handling it. Gonzalo wrote on fltk.general on Feb 21 2014: --------------------------------------------------------------------- I have a GLWindow that draws a lot of stuff.  I am trying to draw text using the fltk functions.  I am able to draw the text properly, but it is always drawn in white.  It does not respect any glColor3f() or glsetcolor() function. My code looks like:    // Turn on Color Buffer and Depth Buffer    glColorMask(true, true, true, true);    // Only write to the Stencil Buffer where 1 is not set    glStencilFunc(GL_NOTEQUAL, 1, 0xFFFFFFFF);    // Keep the content of the Stencil Buffer    glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);    glDisableClientState(GL_TEXTURE_COORD_ARRAY);    glDisable(GL_TEXTURE_2D);    glBegin( GL_BLEND );    // So compositing works properly    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);    glColor4f( r, g, b, a );    fltk::glsetfont(font(), size() );    fltk::gldrawtext(text().c_str(), pts[0].x, pts[0].y); I am able to get colors into the font if I add a glBegin(GL_POLYGON) and glEnd() in between the fltk::gl* calls, but then the text is all garbage.  I looked into gldrawtext() and glsetfont() for clues and nothing is strange. --------------------------------------------------------------------- ..and followed that up with: --------------------------------------------------------------------- I tried it on Linux (where I get white letters) and on Windows (where I get nothing at all ). [..] I found the Linux code suffers from the texture generation from GL_LUMINANCE instead of GL_LUMINANCE_ALPHA. And the glBlendFunc(GL_ONE) instead of GL_SRC_ALPHA. The Windows part of the code I am still digging. ---------------------------------------------------------------------
	#2  greg.ercolano 12:09 Mar 09, 2014	Attached a patch provided by gonzalo that he says: ---- FLTK2.0 patch to make antialiased text in Linux and aliased text in Windows ---- There are some extraneous mods included in the patch, but worthy of note are mods to OpenGL/gl_draw.cxx, in particular this mod caught my eye: -    wglUseFontBitmaps(hdc, base, size, listbase+base); + +    bool succeed = false; +    int MAX_TRIES = 5; +    for ( int i = 0; i < MAX_TRIES && !succeed; ++i ) +    { +       succeed = wglUseFontBitmaps(hdc, base, len, listbase+base) == TRUE; +    } +    if ( !succeed ) +    { +       fprintf( stderr, "wglUseFontBitmaps error\n" ); +    } Suggesting we use fltk::warning() in place of the fprintf(), and I asked gonzalo about the MAX_TRIES loop around wglUseFontBitmaps: ---- erco writes:     Hmm, can you explain what's up with the for() retry loop..     Does it actually need several retries to work? gonzalo answers:     Yes, the for loop is needed as the wgl function sometimes fails unexpectedly     (usually after a change in context). erco follows up:     Thanks -- I see this on the net too, looks like no one seems to know     why it fails, but sometimes it does, so they include the retry loop.     I guess I should make this change in 1.3 as well.     [..]     This is some perhaps relevant info on the issue above.     The MSDN docs for this function:     http://msdn.microsoft.com/en-us/library/windows/desktop/dd374392%28v=vs.85%29.aspx     ..includes a "community comment" that sounds like it might be the reason     it fails on the first try, but succeeds on the second try; it reads:     ________________________________________________________________________________ _______     wglUseFontBitmaps fails if any GL_ERROR is set before calling this function.     We have to call glGetError() before calling this function.     Example:         // Forcefully setting an error.         // Following code is added to demonstrate the problem         glMatrixMode(GL_TEXTURE_2D); // Set opengl Error since matrix         bool bReturnValue = wglUseFontBitmaps( m_hDC, 0,256, m_nFontDisplayList );                                      // bReturnValue returns false, glGetError() return GL_NO_ERROR.     Here Font display list is not created, and error status is not provided by wglUseFontBitmaps.     This problem can be solved by calling glGetError() before wglUseFontBitmaps().         // Forcefully setting an error.         // Following code is added to demonstrate the problem         glMatrixMode(GL_TEXTURE_2D);         int nErr = glGetError();         bool bReturnValue = wglUseFontBitmaps( m_hDC, 0,256, m_nFontDisplayList );     bReturnValue is true and bitmap is created.     ________________________________________________________________________________ _______     [..] so perhaps doing a glGetError() before the call to wglUseFontBitmaps()     will ensure it works the first time. ----

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