Core dump in StelQGLRenderer

[Sibi Antony]

Noticed an arithmetic exception and a core dump with the recent changes. A division by zero in StelQGLRenderer.cpp.

Program terminated with signal 8, Arithmetic exception.
#0 0x00000000005ddd03 in StelQGLRenderer::drawTextGravityHelper (this=0x187ac60, params=..., painter=..., baseX=1018, baseY=525, projector=...)
    at /home/sibi/TUM/IDP/stellarium/stellarium_11.2/stellarium/src/core/renderer/StelQGLRenderer.cpp:271
271 const float charWidth = painter.fontMetrics().width(string) / charCount;

(gdb) bt
#0 0x00000000005ddd03 in StelQGLRenderer::drawTextGravityHelper (this=0x187ac60, params=..., painter=..., baseX=1018, baseY=525, projector=...)
    at /home/sibi/TUM/IDP/stellarium/stellarium_11.2/stellarium/src/core/renderer/StelQGLRenderer.cpp:271
#1 0x00000000005de5d8 in StelQGLRenderer::drawText (this=0x187ac60, params=...)
    at /home/sibi/TUM/IDP/stellarium/stellarium_11.2/stellarium/src/core/renderer/StelQGLRenderer.cpp:349
#2 0x000000000081064f in TextUserInterface::draw (this=0x3464860, core=0x1d0d990, renderer=0x187ac60)
    at /home/sibi/TUM/IDP/stellarium/stellarium_11.2/stellarium/plugins/TextUserInterface/src/TextUserInterface.cpp:610
#3 0x000000000058ac93 in StelModule::drawPartial (this=0x3464860, core=0x1d0d990, renderer=0x187ac60)

Would be good to check the string size before going ahead. Something like this.

  const int charCount = string.length();
+
+ if (!charCount)
+ {
+ return;
+ }
+
  const float charWidth = painter.fontMetrics().width(string) / charCount;

Or better yet, check the string params in drawText().
The TUI plugin forwarded an empty string for selected object (no object selected and empty). So perhaps some optimization in there too.

- if (selectedObj.isEmpty()) {
- objInfo = "";
- } else {
+ if (!selectedObj.isEmpty()) {
                        objInfo = selectedObj[0]->getInfoString(core, tuiInfo);
                        objInfo.replace("\n"," ");
                        objInfo.replace("Distance:"," ");
                        objInfo.replace("Light Years","ly");

                        if (fovMaskDisk) {
                                text_x = xVc + fovOffsetX - pixOffset;
                                text_y = yVc + fovOffsetY - pixOffset;
                        }

                        renderer->setFont(font);
                        renderer->setGlobalColor(0.3f, 1.0f, 0.3f);
                        TextParams params = TextParams(text_x, text_y, objInfo)
                                            .projector(core->getProjection(StelCore::FrameJ2000));
                        if(tuiGravityUi){params.useGravity();}
                        renderer->drawText(params);
                }