IViewObject::GetColorSet - OLE Programmer's Reference

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IViewObject::GetColorSet

Returns the logical palette that the object will use for drawing in its IViewObject::Draw method with the corresponding parameters.

HRESULT GetColorSet(

DWORD dwAspect,	//Specifies how the object is to be represented
LONG lindex,	//Specifies the part of the object to draw
void * pvAspect,	//Always NULL
DVTARGETDEVICE * ptd,	//Specifies the target device in a structure
HDC hicTargetDev,	//Specifies the information context for the target device ptd
LOGPALETTE ** ppColorSet	//Points to LOGPALETTE structure
);

Parameters
dwAspect

[in]Specifies how the object is to be represented. Representations include content, an icon, a thumbnail, or a printed document. Valid values are taken from the enumeration DVASPECT. See the DVASPECT enumeration for more information.

lindex

[in]Indicates the portion of the object that is of interest for the draw operation. Its interpretation varies with dwAspect. See the DVASPECT enumeration for more information.

pvAspect

[in]Provides more information about the view of the object specified in dwAspect. Since none of the current aspects support additional information; pvAspect must always be NULL.

ptd

[in]Points to the target device structure that describes the device for which the object is to be rendered. If NULL, the view should be rendered for the default target device (typically the display). A value other than NULL is interpreted in conjunction with hicTargetDev and hdcDraw. For example, if hdcDraw specifies a printer as the device context, ptd points to a structure describing that printer device. The data may actually be printed if hicTargetDev is a valid value or it may be displayed in print preview mode if hicTargetDev is NULL.

hicTargetDev

[in]Specifies the information context for the target device indicated by the ptd parameter from which the object can extract device metrics and test the device's capabilities. If ptd is NULL, the object should ignore the hicTargetDev parameter.

ppColorSet

[out]Points to location where a LOGPALETTE structure is returned. The LOGPALETTE structure contains the set of colors that would be used if IViewObject::Draw were called with the same parameters for dwAspect, lindex, pvAspect, ptd, and hicTargetDev. A NULL pointer to the LOGPALETTE structure means that the object does not use a palette.

Return Values
S_OK

The set of colors was returned successfully.

S_FALSE

Set of colors is empty or the object will not give out the information.

E_INVALIDARG

One or more arguments are invalid.

OLE_E_BLANK

No presentation data for object.

E_UNEXPECTED

An unexpected error occurred.

DV_E_LINDEX

Invalid value for lindex; currently only -1 is supported.

DV_E_DVASPECT

Invalid value for dwAspect.

Comments
The IViewObject::GetColorSet method recursively queries any nested objects and returns a color set that represents the union of all colors requested. The color set eventually percolates to the top-level container that owns the window frame. This container can call IViewObject::GetColorSet on each of its embedded objects to obtain all the colors needed to draw the embedded objects. The container can use the color sets obtained in conjunction with other colors it needs for itself to set the overall color palette.

The OLE-provided implementation of IViewObject::GetColorSet looks at the data it has on hand to draw the picture. If CF_DIB is the drawing format; the palette found in the bitmap is used. For a regular bitmap; no color information is returned. If the drawing format is a metafile, the object handler enumerates the metafile looking for a CreatePalette metafile record. If one is found; the handler uses it as the color set.

Note to Implementors
Object applications that rely on the default handler for drawing and that use metafiles for doing so should provide a SetPaletteEntries record when they generate their metafiles. If a SetPaletteEntries record is not found; the default object handler returns S_FALSE.

See Also
DVASPECT

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