Version 9 (modified by 16 years ago) ( diff ) | ,
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RFC 18: OGR Style Support in C API
Author: Daniel Morissette
Contact: dmorissette@…
Status: Adopted (2007-12-05)
Summary
OGR has a number of C++ classes that deal with the encoding of style information and attaching that to features. More information is available in the http://www.gdal.org/ogr/ogr_feature_style.html document.
With GDAL/OGR version 1.4.x and older, it was not possible to deal with style information using the C API. This RFC proposes the addition of functions to the C API to manipulate style information in GDAL/OGR 1.5.
Implementation Details
- The following enums will be moved from ogr_featurestyle.h to ogr_core.h:
OGRSTClassId; OGRSTUnitId; OGRSTPenParam; OGRSTBrushParam; OGRSTSymbolParam; OGRSTLabelParam;
- The OGRStyleMgrH (corresponding to the OGRStyleMgr C++ class) will be added to the C API:
OGRStyleMgrH OGR_SM_Create() void OGR_SM_Destroy(OGRStyleMgrH hSM) const char *OGR_SM_InitFromFeature(OGRStyleMgrH hSM) int OGR_SM_InitFromStyleString(const char *pszStyleString) int OGR_SM_GetPartCount(OGRStyleMgrH hSM) OGRStyleToolH OGR_SM_GetPart(OGRStyleMgrH hSM) int OGR_SM_AddPart(OGRStyleMgrH hSM, OGRStyleTool *sPart)
- The OGRStyleToolH (corresponding to the OGRStyleTool C++ class) will be added to the C API:
OGRStyleToolH OGR_ST_Create(OGRSTClassId eClassId) void OGR_ST_Destroy(OGRStyleToolH hST) OGRSTClassId OGR_ST_GetType(OGRStyleToolH hST) OGRSTUnitId OGR_ST_GetUnit(OGRStyleToolH hST) void OGR_ST_SetUnit(OGRStyleToolH hST, OGRSTUnitId eUnit, double dfGroundPaperScale) int OGR_ST_GetParamIsNull(OGRStyleToolH hST, int eParam) const char *OGR_ST_GetParamStr(OGRStyleToolH hST, int eParam) int OGR_ST_GetParamNum(OGRStyleToolH hST, int eParam) double OGR_ST_GetParamDbl(OGRStyleToolH hST, int eParam) void OGR_ST_SetParamStr(OGRStyleToolH hST, int eParam, const char *pszParamString) void OGR_ST_SetParamNum(OGRStyleToolH hST, int eParam, int nParam) void OGR_ST_SetParamDbl(OGRStyleToolH hST, int eParam, double dfParam) const char *OGR_ST_GetStyleString(OGRStyleToolH hST) int OGR_ST_GetRGBFromString(OGRStyleToolH hST, const char *pszColor, int *nRed, int *nGreen, int *nBlue, int *nAlpha);
Note: at implementation time, the OGR_ST_GetParamIsNull() has been removed and replaced by an 'int *bValueIsNull' argument on all the OGR_ST_GetParam...() functions in order to map more closely to the C++ methods.
- NO wrappers will be needed for the following C++ classes which are handled internally by the OGR_ST_* wrappers above:
class OGRStylePen : public OGRStyleTool class OGRStyleBrush : public OGRStyleTool class OGRStyleSymbol : public OGRStyleTool class OGRStyleLabel : public OGRStyleTool
- Note that ogr_featurestyle.h also contains a OGRSTVectorParam enum and a corresponding OGRStyleVector class but this class is currently unused and may eventually be removed, so we will not implement support for it in the C API (and the OGRSTVectorParam enum will NOT be moved to ogr_core.h).
Python and other language bindings
The initial implementation will be for the C API only and will not be ported/tested with the Python and other scripting language bindings. This will have to wait for a later release.
Implementation
Daniel Morissette will implement the changes to the C API described in this RFC for the GDAL/OGR 1.5.0 release.
The first test of the new C API functions will be the conversion of MapServer's mapogr.cpp to use them.
Related Ticket(s)
Voting History
+1 from all PSC members (FrankW, DanielM, HowardB, TamasS, AndreyK)