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| -rw-r--r-- | vcl/inc/sallayout.hxx | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/vcl/inc/sallayout.hxx b/vcl/inc/sallayout.hxx index c46c272376ca..ad6cd9479ab5 100644 --- a/vcl/inc/sallayout.hxx +++ b/vcl/inc/sallayout.hxx @@ -158,6 +158,33 @@ typedef sal_uInt32 sal_GlyphId; // all positions/widths are in font units // one exception: drawposition is in pixel units +// Unfortunately there is little documentation to help implementors of +// new classes derived from SalLayout ("layout engines"), and the code +// and data structures are far from obvious. + +// For instance, I *think* the important virtual functions in the +// layout engines are called in this order: + +// * InitFont() +// * LayoutText() +// * AdjustLayout(), any number of times (but presumably +// usually not at all or just once) +// * Optionally, DrawText() + +// Functions that just return information like GetTexWidth() and +// FillDXArray() are called after LayoutText() and before DrawText(). + +// Another important questions is which parts of an ImplLayoutArgs can +// be changed by callers between LayoutText() and AdjustLayout() +// calls. It probably makes sense only if one assumes that the "string +// related inputs" part are not changed after LayoutText(). + +// But why use the same ImplLayoutArgs structure as parameter for both +// LayoutText() and AdjustLayout() in the first place? And why +// duplicate some of the fields in both SalLayout and ImplLayoutArgs +// (mnMinCharPos, mnEndCharPos, mnLayoutFlags==mnFlags, +// mnOrientation)? Lost in history... + class VCL_PLUGIN_PUBLIC SalLayout { public: |