odoo_source/addons/mail/static/src/xml/composer.xml

<?xml version="1.0" encoding="UTF-8"?>
<templates xml:space="preserve">

     <div t-name="mail.ChatComposer" class="o_chat_composer">
         <div class="o_composer_attachments_list"/>
         <t t-if="widget.extended">
             <div class="o_composer_subject">
                 <input tabindex="1" type="text" class="o_input" placeholder="Subject"></input>
                 <div class="btn-group o_composer_buttons">
                    <button tabindex="3" class="btn btn-sm btn-primary o_composer_button_send" type="button"><t t-esc="widget.options.send_text"/></button>
                    <button tabindex="4" class="btn btn-sm btn-icon fa fa-smile-o o_composer_button_emoji" type="button" data-toggle="popover"/>
                    <button tabindex="5" class="btn btn-sm btn-icon fa fa-paperclip o_composer_button_add_attachment" type="button"/>
                 </div>
             </div>
         </t>
         <div t-attf-class="o_composer #{widget.extended ? 'o_extended_composer' : ''}">
             <div class="o_composer_input">
                 <textarea class="o_input o_composer_text_field" tabindex="2" placeholder="Write something..."/>
             </div>
             <t t-if="!widget.extended">
                 <div class="btn-group o_composer_buttons">
                    <button tabindex="3" class="btn btn-sm btn-primary o_composer_button_send" type="button"><t t-esc="widget.options.send_text"/></button>
                    <button tabindex="4" class="btn btn-sm btn-icon fa fa-smile-o o_composer_button_emoji" type="button" data-toggle="popover"/>
                    <button tabindex="5" class="btn btn-sm btn-icon fa fa-paperclip o_composer_button_add_attachment" type="button"/>
                 </div>
             </t>
         </div>

         <span class="hide">
            <t t-call="HiddenInputFile">
                <t t-set="fileupload_id" t-value="widget.fileupload_id"/>
                <t t-set="fileupload_action" t-translation="off">/web/binary/upload_attachment</t>
                <t t-set="multi_upload" t-value="true"/>
                <input type="hidden" name="model" value="mail.compose.message"/>
                <input type="hidden" name="id" value="0"/>
                <input type="hidden" name="session_id" t-att-value="widget.getSession().session_id"/>
            </t>
         </span>
         <span t-att-class="widget.emoji_container_classname"></span>
    </div>

    <t t-name="mail.ChatComposer.emojis">
        <t t-foreach="emojis" t-as="emoji">
            <span t-att-data-emoji="emoji.source" class="o_mail_emoji" t-att-title="emoji.description">
                <t t-raw="emoji.substitution"/>
            </span>
        </t>
    </t>

    <t t-name="mail.AbstractMentionSuggestions">
        <ul class="dropdown-menu" aria-labelledby="dropdownMailMentionMenu">
            <t t-foreach="suggestions" t-as="suggestion">
                <li t-if="suggestion.divider" class="divider"/>
                <li t-if="!suggestion.divider" class="o_mention_proposition" t-att-data-id="suggestion.id">
                    <a href="#"/>
                </li>
            </t>
        </ul>
    </t>
    <t t-name="mail.MentionPartnerSuggestions" t-extend="mail.AbstractMentionSuggestions">
        <t t-jquery=".o_mention_proposition a" t-operation="append">
            <span class="o_mention_name"><t t-esc="suggestion.name"/></span>
            <t t-if="suggestion.email">
                <span class="o_mention_info">(<t t-esc="suggestion.email"/>)</span>
            </t>
        </t>
    </t>
    <t t-name="mail.MentionChannelSuggestions" t-extend="mail.AbstractMentionSuggestions">
        <t t-jquery=".o_mention_proposition a" t-operation="append">
            <span class="o_mention_name"><t t-esc="suggestion.name"/></span>
        </t>
    </t>
    <t t-name="mail.MentionCannedResponseSuggestions" t-extend="mail.AbstractMentionSuggestions">
        <t t-jquery=".o_mention_proposition a" t-operation="append">
            <span class="o_mention_name"><t t-esc="suggestion.source"/></span>
            <span class="o_mention_info"><t t-esc="suggestion.substitution"/></span>
        </t>
    </t>
    <t t-name="mail.MentionCommandSuggestions" t-extend="mail.AbstractMentionSuggestions">
        <t t-jquery=".o_mention_proposition a" t-operation="append">
            <span class="o_mention_name">/<t t-esc="suggestion.name"/></span>
            <span class="o_mention_info"><t t-esc="suggestion.help"/></span>
        </t>
    </t>

</templates>