Hi, 

I'm trying to porting v8 report addon to v11. 

I applied every changes in odoo 11 but I have to misunderstood somethings. My report downloading but blank page. I didn't understand what i missed. 

here is my code;

report/wizard_account_partner_balance_letter.py

class AccountPartnerBalanceLetter(models.TransientModel):

    _name = 'account.partner.balance.letter'

    date_start = fields.Date(string='Date Start', default=datetime(2011, 1, 1).date())

    date_end = fields.Date(string='Date End', default=datetime.now().date())

    @api.multi

    def print_report(self):

        """

        :return:

        """

        data = {

            'ids': self.ids,

            'form': self.read()[0],

        }

        return self.env.ref('l10n_tr_account_partner_balance_letter.action_report_account_partner_balance_letter').report_action([], data=data)

wizard/wizard_account_balance_letter.xml

<?xml version="1.0" encoding="utf-8"?>

<odoo>

    <data>

        <record id="wizard_account_partner_balance_letter_form" model="ir.ui.view">

            <field name="name">wizard.account.partner.balance.letter.form</field>

            <field name="model">account.partner.balance.letter</field>

            <field name="type">form</field>

            <field name="arch" type="xml">

                <form string="Account Partner Balance Letter">

                    <group colspan="2">

                        <field name="date_start" invisible="1"/>

                        <field name="date_end"/>

                    </group>

                    <footer>

                        <button name="print_report" string="Print" type="object" class="oe_highlight"

                                context="{'date_from':date_start, 'date_to':date_end}"/>

                        or

                        <button string="Cancel" special="cancel" class="oe_link"/>

                    </footer>

                </form>

            </field>

        </record>

        <record id="account_partner_balance_letter_action_window" model="ir.actions.act_window">

            <field name="name">Account Partner Balance Letter</field>

            <field name="res_model">account.partner.balance.letter</field>

            <field name="view_type">form</field>

            <field name="view_mode">form</field>

            <field name="view_id" ref="wizard_account_partner_balance_letter_form"/>

            <field name="target">new</field>

        </record>

        <menuitem id="menu_partner_balance_letter"

                  name="Account Partner Balance Letter"

                  parent="account_reports.account_reports_audit_reports_menu"

                  action="account_partner_balance_letter_action_window"/>

    </data>

</odoo>

<?xml version="1.0" encoding="utf-8"?>

<odoo>

    <data>

        <report

            id="action_report_account_partner_balance_letter"

            string="Mutabakat Mektubu"

            model="res.partner"

            report_type="qweb-pdf"

            menu="False"

            name="l10n_tr_account_partner_balance_letter.report_res_partner"

            file="l10n_tr_account_partner_balance_letter.report_res_partner"

        />

        <record forcecreate="True" id="paperformat_partner_balance_letter_reporting" model="report.paperformat">

            <field name="name">Partner Balance Letter Paperformat</field>

            <field name="default" eval="True"/>

            <field name="format">A4</field>

            <field name="page_height">0</field>

            <field name="page_width">0</field>

            <field name="orientation">Portrait</field>

            <field name="margin_top">5</field>

            <field name="margin_bottom">0</field>

            <field name="margin_left">10</field>

            <field name="margin_right">10</field>

            <field name="header_line" eval="True"/>

            <field name="header_spacing">0</field>

            <field name="dpi">90</field>

        </record>

    </data>

</odoo>