GreMultiplyXforms

GreMultiplyXforms multiplies the transform matrix.

This function can be hooked by the presentation driver.

Simulation support

This function is simulated by a handling routine in the graphics engine.

Syntax

GreMultiplyXforms(hdc, paXform, paNewXformData, lMode, pInstance, lFunction);

Parameters

hdc (HDC) - input

Device context handle.

paXform (PXFORM) - output

On input: Transform used during lMode operation.

On output: Result of the lMode operation.

paNewXformData (PXFORM) - input

Transform used during lMode operation.

lMode (LONG) - input

Specifies how supplied array is used to set matrix:

• SX_UNITY Set unity transform, ignore array values
• SX_CAT_AFTER Concatenate after
• SX_CAT_BEFORE Concatenate before
• SX_OVERWRITE Overwrite

pInstance (PVOID) - input

Pointer to instance data.

lFunction (ULONG) - input

High-order WORD=flags; low-order WORD=NGreMultiplyXforms.

Return Code

fSuccess (BOOL) - returns

Return codes.

This function returns BOOLEAN (fSuccess).

• TRUE Successful
• FALSE Error

Possible Errors Detected: When an error is detected, the handling routine must call WinSetErrorInfo to post the condition. Error codes for conditions that the handling routine is expected to check include:

• PMERR_INV_MATRIX_ELEMENT
• PMERR_INV_TRANSFORM_TYPE

Refer to the "Error Explanations" section in the Presentation Manager Programming Reference for further explanation.

Remarks

This function multiplies the transform matrix (defined by paNewXformData) by the corresponding matrix in paXform. The result is stored in paXform. When this function is used to make a series of matrix multiplications on the same matrix, some loss of accuracy can occur due to rounding because no higher precision can be retained across calls.

Declaration

#define INCL_GRE_XFORMS
#include <os2.h>

HDC       hdc;             /*  Device context handle. */
PXFORM    paXform;
PXFORM    paNewXformData;
LONG      lMode;           /*  Specifies how supplied array is used to set matrix: */
PVOID     pInstance;       /*  Pointer to instance data. */
ULONG     lFunction;
BOOL      fSuccess;        /*  Return codes. */

fSuccess = GreMultiplyXforms(hdc, paXform,
             paNewXformData, lMode, pInstance,
             lFunction);