FIX for gtkglext

[ovhpa]

This is an important fix for distributions which use a gtkglext version for which gdk_gl_font_use_pango_font have been removed.

The root of the problem was the removal of gdk_gl_font_use_pango_font which had no actual (or practical) replacement. It impacted and continue to impact several package (including ghemical until now and gabedit on some distributions, both of which I sometimes use).

I choose to use a method which involves pango + cairo writing the text onto a buffer, then draw that buffer on the screen directly using glDrawPixels. This may not be the recommended method (according to forums writing text on a texture then placing it on the screen is better) but I think it is more appropriate.

Also the openGL part of the code:

glRasterPos3f(x,y,z);
glPixelZoom( 1, -1 );
glDrawPixels(width,height,GL_BGRA,GL_UNSIGNED_BYTE,surface_data);

is close to the original:

glRasterPos3f(x,y,z); 
glListBase(font_offset);
glCallLists(strlen(str), GL_UNSIGNED_BYTE, str);

The added glPixelZoom is required because for some reason glDrawPixels draw the buffer upside-down. ^^'

• This (I think) will allow users to install GDIS on most Linux distributions, regardless of the gtkglext version. For example the installation on Opensuse was really troublesome.
• The other benefit is that error message GdkGLExt-WARNING **: cannot load PangoFont will not appear and all text will actually be displayed. The fonts are used "on time" and not preloaded, so it would even be theoretically possible to use several fonts on the same structure.
• Additionally, all fonts that can be list on GDIS font selection dialogue will now be available. On some distributions / configurations, only few fonts could actually display some text.
• Last but not least, the text display is now of pango_layout_set_markup type, which means we can add dynamical text that contain pango markup language. So we could have a ¹⁴C labelled atom :D

However, should there be some trouble, please let me know.

PS: I'm committing this now, because we require it for the incoming workshop. PPS: I also include some minor fixing (mostly to remove some of the warning messages).

[arohl]

I have struggled with the

• GdkGLExt-WARNING **: cannot load PangoFont

error for some time now. Will be great if it never darkens our door again!

So where is the font actually set and how do I get a list of possible fonts?

[ovhpa]

I think it's gone for good :D Just change the font using GDIS own interface: On menu: View/Display Properties/OpenGL/Change graphics font.

[arohl]

I didn’t know that Sean implemented that! Nice!

On 10 Jun 2019, at 9:28 pm, Okadome Valencia notifications@github.com<mailto:notifications@github.com> wrote:

I think it's gone for good :D Just change the font using GDIS own interface: On menu: View/Display Properties/OpenGL/Change graphics font.