| Summary: | Matrix operations offset draw on widget creation. | ||
|---|---|---|---|
| Product: | cairo | Reporter: | Chris S. Cowles <c_cowles> |
| Component: | general | Assignee: | Chris Wilson <chris> |
| Status: | RESOLVED NOTABUG | QA Contact: | cairo-bugs mailing list <cairo-bugs> |
| Severity: | major | ||
| Priority: | medium | ||
| Version: | unspecified | ||
| Hardware: | x86-64 (AMD64) | ||
| OS: | Linux (All) | ||
| Whiteboard: | |||
| i915 platform: | i915 features: | ||
| Attachments: | Source files illustrating cairo matrix offset bug. | ||
This works as documented. Try using things like cairo_rotate() instead of overwriting the matrix. At least try something like this: cairo_matrix_t matrix, identity_matrix; cairo_get_matrix(cr, &matrix); cairo_matrix_init_identity(&identity_matrix); // This makes no sense, but feel free to replace with a rotation cairo_matrix_multiply(&matrix, &matrix, &identity_matrix); cairo_set_matrix(cr, &matrix); (Technical detail: Gtk is giving you a cairo context onto a large surface and uses the matrix so that it appears to you as if the surface's (0, 0) were at the top-left corner of your widget. If you ignore the matrix, stuff breaks.) |
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Created attachment 118353 [details] Source files illustrating cairo matrix offset bug. When using cairo (version 1.14.3) in creating a widget, matrix use causes image to be offset within the cairo_t. This can be illustrated by drawing with/without an identity matrix. (Matrix is needed for image rotation on widget.) An example is attached. Define "USE_MATRIX" in the header file to turn on the error. Environment used: Debian 4.8.4-1, Linux version 3.16.0-4-amd64, gcc version 4.9.2