GDI Plus Base Foundation Class

Article
07/09/2007

The gpBase class is the abstract base class for all other _GDIPLUS classes and provides some basic utility methods.

Category	Reporting
Default Catalog	Visual FoxPro Catalog\Foundation Classes\Output\GDIplus
Class	gpBase
Base Class	Custom
Class Library	_GDIPLUS.vcx
Parent Class	Custom (Custom Object)

Remarks

The following table lists public properties and methods added by this class to its parent class, Custom.

Properties and methods	Description
AllowModalMessages Property	Determines whether the class is allowed to display modal dialog boxes to provide user feedback. Default`INLIST(_VFP.StartMode,0,4)` Remarks: Affects the UI that error handler presents when QuietOnError is false. If AllowModalMessages=`.T.`, then a modal message box is shown and processing stops. If AllowModalMessages=`.F.`, then a WAIT WINDOW ... NOWAIT command is used and processing continues.
AppName Property	Application name for use in user feedback. Default "`GDI+ FFC Library"`
ClearErrors Method	Resets the object's error status. Syntax: `THIS.ClearErrors()` Return Values: None Parameters: None.
Clone Method	Create a new object as an exact copy of an existing object. Syntax: `THIS.Clone()` Return Values: None Parameters: toClone, required, object to make this object a clone of. Remarks: This function has no meaning in the GpBase class. It is implemented in most subclasses. For objects that wrap an underlying GDI+ object, the underlying object is cloned as well.
GetErrorStatus Method	Indicates whether an error has occurred. Syntax: `lError = THIS.GetErrorStatus()` Return Values: Logical. Parameters: None. Remarks: Returns True (`.T.`) if an error has occurred since the last call to ClearError().
GetLastErrorMessage Method	Provides information about the last error that occurred. Syntax: `cErrorMessage = THIS.getLastErrorMessage()` Return Values: String. cErrorMessage is the text of the last error to occur. Parameters: None. Remarks: The value of cErrorMessage is only valid when GetErrorStatus() returns True (`.T.`).
GUIDToString Method	Converts GUID or CLSID from binary form to human-readable string representation. Syntax: `cGUIDString = THIS.GUIDToString(tqGUID)` Return Values: String, in standard `{abcdefab-cdef–abcd-efab-cdefabcdefab}` format. Returns null (`.NULL.`) if an error occurs. Parameters: tqQUID is the GUID or CLSID to be converted.
IgnoreErrors Property	Indicates whether errors should halt processing. Default`.F.`
MakeGdipArrayF Method	Converts numeric values in a Visual FoxPro array to a binary string, representing a one- or two-dimensional array of float (single-precision) values, suitable for passing directly to native GDI or GDI+ functions. Syntax: `cArrayString = THIS.MakeGdipArrayF(taArray[, tnCols[, tnFirstCol]])` Return Values: Array represented in a string. Each value takes four bytes. The total length of the string is thus (`ALEN(taArray,1) * tnCols4`). Returns null (`.NULL.`) if an error occurs. Parameters:* taArray, required, is an array of number values. Must have at least tnCols. tnCols, optional, is the number of columns to convert. Defaults to the number of values in the array. tnFirstCol, optional, is the first column number to start the conversion. Defaults to 1.
MakeGdipArrayFFromCursor Method	Converts numeric values in a Visual FoxPro cursor to a binary string, representing a one- or two-dimensional array of float (single-precision) values, suitable for passing directly to native GDI or GDI+ functions. Syntax: `cArrayString = THIS.MakeGdipArrayFFromCursor(tcAlias, tnCols, tcExpr1[, tcExpr2[, tcExpr3[, tcExpr4[, tcExpr5[, tcExpr6[, tcExpr7[, tcExpr8]]]]]]])` Return Values: Array represented in a string. Each value takes four bytes. The total length of the string.is thus `(RECCOUNT(tcAlias) * tnCols4)`. Returns null (`.NULL.`) if an error occurs. Parameters:* tcAlias, required, is the alias of a cursor. Must have at least tnCols fields. tnCols, required, is the number of columns the array must have. At least tnCols expressions must be specified in the following parameters. tcExpr1, required, is the expression for the first column (usually a field name). tcExpr2, required if tnCols is >=2, is the expression for the second column (usually a field name). tcExpr3, required if tnCols is >=3, is the expression for the third column (usually a field name). tcExpr4, required if tnCols is >=4, is the expression for the fourth column (usually a field name). tcExpr5, required if tnCols is >=5 is the expression for the fifth column (usually a field name). tcExpr6, required if tnCols is >=6 is the expression for the sixth column (usually a field name). tcExpr7, required if tnCols is >=7 is the expression for the seventh column (usually a field name). tcExpr8, required if tnCols >= 8 is the expression for the eighth column (usually a field name).
MakeGdipPointF Method	Creates GDI+ PointF structure as string, from separate x,y parameters. Syntax: `cString = MakeGdipPointF(tX, tY)` Return Values: 8-byte string representing two float values. Returns null (`.NULL.`) on error. Parameters: tX, required, numeric, the X coordinate of the point. tY, required, numeric, the Y coordinate of the point.
MakeGdipRectF Method	Creates GDI+ RectF structure as string, from separate x,y,w,h parameters. Syntax: `cString = MakeGdipRectF(tX, tY, tW, tH)` Return Values: 16-byte string representing four float values. Returns null (`.NULL.`) on error. Parameters: tX, required, numeric, the X coordinate of the point. tY, required, numeric, the Y coordinate of the point. tW, required, numeric, the Width value (horizontal dimension). tH, required, numeric, the Height value (vertical dimension).
MakeGdipSizeF Method	Creates GDI+ SizeF structure as string, from separate x and y parameters. Syntax: `cString = MakeGdipSizeF(tW, tH)` Return Values: 8-byte string representing two float values. Returns null (`.NULL.`) on error. Parameters: tW, required, numeric, the Width value (horizontal dimension). tH, required, numeric, the Height value (vertical dimension).
ObjFactory Method	Internal function to create _GDIPLUS objects. Used primarily by _GDIPLUS-derived objects' methods that return object values. Syntax: `oObject = ;` `THIS.ObjFactory( tcContext, tcClassname [, p1,p2,p3...p10 ] )` Return Values: The created object. Returns null (`.NULL.`) on error. Parameters: tcContext, string, the context of the object creation, usually a value in the form `"class.methodname"`. tcClassName, string, the name of the class to instantiate. Always one of the base _GDIPLUS classes (such as `"gprect"`). Remarks: This function along with ObjFactoryHook() can be used to change the classes used by the GDI+ foundation classes. Refer to the `GDIPLUS_CLASS_*` constants defined in GDIPLUS.H for default values.
ObjFactoryHook Method	Allows modifications to the class that will be created by ObjFactory(). Syntax: `THIS.ObjFactoryHook( tcContext, @rcClassName, @rcClassLibrary, @rcModule )` Return Values: none. Parameters: tcContext, string, context value passed to ObjFactory(). rcClassName, string, the class that will be created. Assign a value to this parameter to change the class that will be instantiated. rcClassLibrary, string, the default class library in which the class to be created should be found. rcModule, string, the module (.app, .dll or .exe file). By default will be an empty string (`""`).
QuietOnError Property	If True (`.T.`), causes error messages to be suppressed. Default`NOT INLIST(_VFP.StartMode,0,4)`
StringToGUID Method	Converts a human-readable string representation of a GUID or CLSID to binary form. Syntax: `qGUID = THIS.StringToGUID(tcString)` Return Values: qQUID is the GUID or CLSID as a 16-byte varbinary value. Returns null (`.NULL.`) if an error occurs. Parameters: tcString is a human-readable GUID or CLSID in standard `{abcdefab-cdef–abcd-efab-cdefabcdefab}` format.

See Also

Reference

Visual FoxPro Foundation Classes A-Z
GDI Plus API Wrapper Foundation Classes

Concepts

Guidelines for Using Visual FoxPro Foundation Classes