问中messageRead和messageWrite模式的逻辑？

EN

<!-- Message Read -->
    <ExtensionPoint xsi:type="MessageReadCommandSurface">
    <!-- Use the default tab of the ExtensionPoint or create your own with <CustomTab id="myTab"> -->
    <OfficeTab id="TabDefault">
        <!-- Up to 6 Groups added per Tab -->
        <Group id="msgReadGroup">
        <Label resid="groupLabel" />
        <!-- Launch the add-in : task pane button -->
        <Control xsi:type="Button" id="msgReadOpenPaneButton">
            <Label resid="paneReadButtonLabel" />
            <Supertip>
            <Title resid="paneReadSuperTipTitle" />
            <Description resid="paneReadSuperTipDescription" />
            </Supertip>
            <Icon>
            <bt:Image size="16" resid="icon16" />
            <bt:Image size="32" resid="icon32" />
            <bt:Image size="80" resid="icon80" />
            </Icon>
            <Action xsi:type="ShowTaskpane">
            <SourceLocation resid="messageReadTaskPaneUrl" />
            </Action>
        </Control>
        </Group>
    </OfficeTab>
    </ExtensionPoint>


<!-- Message Compose -->
    <ExtensionPoint xsi:type="MessageComposeCommandSurface">
        <OfficeTab id="TabDefault">
            <Group id="msgComposeCmdGroup">
            <Label resid="groupLabel"/>
            <Control xsi:type="Button" id="msgComposeIndex">
                <Label resid="indexLabel"/>
                <Supertip>
                <Title resid="indexTitle"/>
                <Description resid="insertGistDesc"/>
                </Supertip>
                <Icon>
                <bt:Image size="16" resid="icon16"/>
                <bt:Image size="32" resid="icon32"/>
                <bt:Image size="80" resid="icon80"/>
                <bt:Image size="80" resid="paksign"/>

                </Icon>
                <Action xsi:type="ShowTaskpane">
                <SourceLocation resid="index-file" />
                </Action>
            </Control>
            </Group>
        </OfficeTab>
    </ExtensionPoint>