Generated C++ files are not deterministic, making ccache useless

[ubruhin]

Bug Description

The *.cpp files generated from *.slint files are not deterministic. Some struct member initialization code seems to have a random order (maybe coming from an unordered dict?). The problem is that this breaks ccache from being useful, thus wasting time during development.

Example of generated code:

// This file is auto-generated
#include "/home/urban/tmp/slint-cpp-template/build/app-window.h"

auto Button_root_1::init (const class SharedGlobals* globals,slint::cbindgen_private::ItemTreeWeak enclosing_component,uint32_t tree_index,uint32_t tree_index_of_first_child) -> void{
    auto self = this;
    self->self_weak = enclosing_component;
    self->globals = globals;
    this->tree_index_of_first_child = tree_index_of_first_child;
    self->tree_index = tree_index;
    self->root_1_accessible_action_default.set_handler(
                    [this]() {
                        [[maybe_unused]] auto self = this;
                        [&]{ [&]() -> void { if (self->native_3.checkable.get()) { self->native_3.checked.set((! self->native_3.checked.get())); } else { ; }}();self->native_3.clicked.call(); }();
                    });
    self->root_1_empty_2_layout_cache.set_binding([this]() {
                            [[maybe_unused]] auto self = this;
                            return slint::private_api::solve_box_layout([&](const auto &a_0, const auto &a_1, const auto &a_2, const auto &a_3, const auto &a_4){ slint::private_api::BoxLayoutData o{}; o.size = a_0; o.alignment = a_1; o.cells = a_2; o.spacing = a_3; o.padding = a_4; return o; }(self->root_1_width.get(), slint::cbindgen_private::LayoutAlignment::Stretch, slint::cbindgen_private::Slice<slint::cbindgen_private::BoxLayoutCellData>{ std::array<slint::cbindgen_private::BoxLayoutCellData, 1>{ slint::cbindgen_private::BoxLayoutCellData ( [&](const auto &a_0){ slint::private_api::BoxLayoutCellData o{}; o.constraint = a_0; return o; }(SLINT_GET_ITEM_VTABLE(NativeButtonVTable)->layout_info({SLINT_GET_ITEM_VTABLE(NativeButtonVTable), const_cast<slint::cbindgen_private::NativeButton*>(&self->native_3)}, slint::cbindgen_private::Orientation::Horizontal, &self->globals->window().window_handle())) ) }.data(), 1 }, 0, [&](const auto &a_0, const auto &a_1){ slint::private_api::Padding o{}; o.begin = a_0; o.end = a_1; return o; }(0, 0)),slint::cbindgen_private::Slice<int>{ std::array<int, 0>{  }.data(), 0 });
                        });
    self->root_1_empty_2_layoutinfo_h.set_binding([this]() {
                            [[maybe_unused]] auto self = this;
                            return slint::private_api::box_layout_info(slint::cbindgen_private::Slice<slint::cbindgen_private::BoxLayoutCellData>{ std::array<slint::cbindgen_private::BoxLayoutCellData, 1>{ slint::cbindgen_private::BoxLayoutCellData ( [&](const auto &a_0){ slint::private_api::BoxLayoutCellData o{}; o.constraint = a_0; return o; }(SLINT_GET_ITEM_VTABLE(NativeButtonVTable)->layout_info({SLINT_GET_ITEM_VTABLE(NativeButtonVTable), const_cast<slint::cbindgen_private::NativeButton*>(&self->native_3)}, slint::cbindgen_private::Orientation::Horizontal, &self->globals->window().window_handle())) ) }.data(), 1 },0,[&](const auto &a_0, const auto &a_1){ slint::private_api::Padding o{}; o.end = a_0; o.begin = a_1; return o; }(0, 0),slint::cbindgen_private::LayoutAlignment::Stretch);
                        });
    self->root_1_empty_2_layoutinfo_v.set_binding([this]() {
                            [[maybe_unused]] auto self = this;
                            return slint::private_api::box_layout_info_ortho(slint::cbindgen_private::Slice<slint::cbindgen_private::BoxLayoutCellData>{ std::array<slint::cbindgen_private::BoxLayoutCellData, 1>{ slint::cbindgen_private::BoxLayoutCellData ( [&](const auto &a_0){ slint::private_api::BoxLayoutCellData o{}; o.constraint = a_0; return o; }(SLINT_GET_ITEM_VTABLE(NativeButtonVTable)->layout_info({SLINT_GET_ITEM_VTABLE(NativeButtonVTable), const_cast<slint::cbindgen_private::NativeButton*>(&self->native_3)}, slint::cbindgen_private::Orientation::Vertical, &self->globals->window().window_handle())) ) }.data(), 1 },[&](const auto &a_0, const auto &a_1){ slint::private_api::Padding o{}; o.end = a_0; o.begin = a_1; return o; }(0, 0));
                        });
    self->native_3.checkable.set_binding([this]() {
                            [[maybe_unused]] auto self = this;
                            return false;
                        });
    self->native_3.enabled.set_binding([this]() {
                            [[maybe_unused]] auto self = this;
                            return true;
                        });
}

Lines 17 and 25 contain random content:

slint::private_api::BoxLayoutData o{}; o.size = a_0; o.alignment = a_1; o.cells = a_2; o.spacing = a_3; o.padding = a_4; return o;
slint::private_api::BoxLayoutData o{}; o.cells = a_0; o.spacing = a_1; o.padding = a_2; o.alignment = a_3; o.size = a_4; return o;

Another case are embedded resources in the generated *.h files, which seem to be random too:

This is actually much worse as the generated header file will be included in many *.cpp files, causing ccache to fail on all those files too. In LibrePCB this currently leads to ~60 seconds of wasted time on every unnecessary rebuild.

I suspect this problem should be easy to fix, but would save a lot of time (and nerves).

Note that I can't say if there are more cases than the two mentioned, but I'd be happy to try again and report once these two are fixed.

Reproducible Code (if applicable)

Environment Details

• Slint Version: Current master
• Platform/OS: Linux
• Programming Language: C++
• Backend/Renderer:

Product Impact

No response

[ogoffart]

Thanks for the bug report. This should indeed be fixed. Probably some HashMap can be replaced by BTreeMap