It's like this ..... I have an external arppegiator triggering my synth... I click my left/right arrows to change preset.... and because I use a custom data model, I have to tap into the pre/post callbacks.... so here's what I get:

synth notes triggering.... click the arrow....
Interface: preLoadCallback triggered - no synth notes triggering when this is running
Interface: onPresetLoad triggered - no synth notes triggering when this is running
Once the onPresetLoad method is finished, a midi note does sneak through into the synth....

Then this callback fires:
Interface: postLoadCallback triggered
This kills the previous notes, and triggers the new ones.....

Here is my full loadGlobalPreset method:

inline function loadGlobalPreset(obj) {
        local samplemaps = obj.samplemaps;
        local wavetables = obj.wavetables;
        local params = obj.parameters;
        local fxSelections = obj.fxSelections;
        local fxChainOrder = obj.fxChainOrder;

        lastLoadParams = params;

        // Restore samplemaps
        UISoundSelector.syncSamplerMenu(1, samplemaps[0]);
        UISoundSelector.syncSamplerMenu(2, samplemaps[1]);
        UISoundSelector.syncSamplerMenu(3, samplemaps[2]);

        // Restore wavetables
        UISoundSelector.syncSynthMenu(1, wavetables[0]);
        UISoundSelector.syncSynthMenu(2, wavetables[1]);
        UISoundSelector.syncSynthMenu(3, wavetables[2]);

        // Update all UI parameters - except the ones that are not tagged as saveInPreset
        UserPresetHandler.updateSaveInPresetComponents(params);

        // TODO: Restore custom samples

        // Fix-up FX menus by stable id, but only when they differ
        if (isDefined(fxSelections)) {
            for (i = 0; i < fxSelections.length; i++) {
                local sel = fxSelections[i];
                if (!isDefined(sel) || !isDefined(sel.id)) continue;

                local targetId = (isDefined(sel.idName) && sel.idName != "") ? sel.idName : "empty";

                local menu = Content.getComponent(sel.id);
                if (!isDefined(menu)) continue;

                // what saveInPreset restored (by index)
                local currentId = UIEffectDropDownMenu.getIdForIndex(menu.getValue());
                if (currentId == undefined) currentId = "empty";

                // only fire callback if mismatch
                if (currentId != targetId)
                    UIEffectDropDownMenu.setMenuToId(sel.id, targetId, true);
            }
        }

        // Restore FX chain ordering (pageKey -> [4 slots])
        if (isDefined(fxChainOrder)) {
            for (k in fxOrderKeys) {
                local key = fxOrderKeys[k];
                local saved = fxChainOrder[key];

                // expect an array of length 4 with unique 0..3
                if (!isDefined(saved) || saved.length != 4) continue;

                UIEffectReordering.pageOrder[key] = saved;          // update UI state
                UIEffectReordering.applyVisualOrder(key);           // move panels
                PluginEffectReorder.apply(key, saved);              // set DSP chain
            }
        }

        // Update all UI parameters - except the ones that are not tagged as saveInPreset
        //UserPresetHandler.updateSaveInPresetComponents(params);
    }

It is doing quite a lot... and ultimately what happens is when I switch a preset, I get one voice that sounds one way... and then another voice that sounds completely different... like a voice is being allowed to be triggered before the preset is fully loaded.

It seems to be something related to my effect menus and/or effect re-ordering.

It is hard to explain. Might have to make a video. But any immediate thoughts??

Why do you want to do this?

Because it kills voices and I want to silently update some metadata like tags and author for presets.

But.... your method seems to be working!!! I feel like I'm going to have to remove certain characters in case it messes up the preset code....

@ustk ok got it working. Is it possible to update the .preset file without using Engine.saveUserPreset ?

Why do you want to do this?

I'm doing this when I save my custom fx chain format:

inline function saveFXChainPreset() {
        FileSystem.browse(FileSystem.getFolder(FileSystem.UserPresets), true, "*.fxchain", function (f) {
            if (!isDefined(f) || f == 0) return;

            PluginSharedData.presetMode = "FXChain";

            // Get the data object directly from our custom save logic
            var data = PluginUserPresetHandling.onPresetSave();
            f.writeObject(data);
        });
    }

the key being setup a file reference, and then call f.writeObject(blahblah) on it.

that's what I do a lot in the things I've worked on

of course Ok I'm obviously passing the data in wrong. Will take another look...

@ustk clever - but possibly running through all the presets every time you load a new preset is going to take a while.... I'd need to cache them somehow.

No, only at init when for checking if new presets are present

How does saving panel data work? Do you have to save the preset (bad for my use case)? Does it auto update / write to the .preset file?

Yes true... but it should be possible to just write it in the preset dynamically without the need to save. but that would require some clever string handling, don't know if it's secure enough and/or doable, but that might worth a try...
That might be where the already existing custom preset system is better...

Where is the data in the .preset file?!

Under the panel's value, like all other components

EDIT - Oh it's not persistant... doh

Yes it is if in the preset..., it's recalled like any other value, that's what I do a lot in the things I've worked on

How does saving panel data work? Do you have to save the preset (bad for my use case)? Does it auto update / write to the .preset file? Where is the data in the .preset file?!

EDIT - Oh it's not persistant... doh

Calling:
updateSaveInPresetComponents(params) does indeed have the effect of setting any non specified parameters to their default value. This is not optimal for all use cases, for example my fx chain use case. Because what is happening is my synthesis generators are being reset to their default state, and the only way I can see how to avoid this is by iterating over all controls I do want to edit, and calling .setValue and then .changed() on them... which is actually quite slow it turns out.

Could anything be done about this???

Basically, you've got this:

namespace PluginUserPresetHandling {

    const UserPresetHandler = Engine.createUserPresetHandler();

    inline function onPresetSave() // this is your main preset save method
    {
        Console.print("onPresetSave triggered");
    }

    inline function onPresetLoad(obj) // this is your main preset load method
    {
        Console.print("onPresetLoad triggered");
    }

    inline function preLoadCallback() // things you want to happen before loading a preset happen here - looking for samples, looking for graphical assets, etc.
    {
        Console.print("preLoadCallback triggered");
    }

    inline function postLoadCallback() // things you want to happen after loading a preset happen here - updating preset name labels in your UI, triggering other UI updates, etc.
    {
        Console.print("postLoadCallback triggered");
    }

    inline function postSaveCallback() // things you want to happen after saving a preset happen here - copying samples to an external location, removing any dirty flags you might've setup in the UI layer, etc.
    {
        Console.print("postSaveCallback triggered");
    }


    inline function init() {
        UserPresetHandler.setUseCustomUserPresetModel(onPresetLoad, onPresetSave, false); // this line is essential
        UserPresetHandler.setPreCallback(preLoadCallback);
        UserPresetHandler.setPostCallback(postLoadCallback);
        UserPresetHandler.setPostSaveCallback(postSaveCallback);
    }
}

You can achieve a hell of a lot with this, without discarding the HISE preset system.

For example, here is my onPresetSave method in my current project:

    inline function onPresetSave() {
        Console.print("onPresetSave triggered");
        PluginSharedHelpers.forceAllOuterSlotsEnabled();

        if (PluginSharedData.presetMode == "Global") {
            return saveGlobalPreset();
        }
        if (PluginSharedData.presetMode == "FXChain") {
            return saveFXChain();
        }
    }

In this way, I'm able to gate different save functions based on a master type, which means I can either write the HISE .preset file, or I can write a custom file using my own data model.

My load one is this:
inline function onPresetLoad(obj) {
Console.print("onPresetLoad triggered");
PluginSharedData.isRestoringPreset = true;

    if (PluginSharedData.presetMode == "Global") {
        loadGlobalPreset(obj);
    }
    if (PluginSharedData.presetMode == "FXChain") {
        loadFXChain(obj);
    }

    PluginSharedData.isRestoringPreset = false;
}

The loadFXchain method is this:

inline function loadFXChain(obj) {
        if (!isDefined(obj)) return;

        Console.print("we are now attempting to load an fx chain");
        PluginSharedHelpers.forceAllOuterSlotsEnabled();

        local fxSelections = obj.fxSelections;
        local fxChainOrder = obj.fxChainOrder;
        local params = obj.parameters;

        // Set effect menus by stable id (this loads the networks)
        if (isDefined(fxSelections)) {
            for (i = 0; i < fxSelections.length; i++) {
                local sel = fxSelections[i];
                if (!isDefined(sel) || !isDefined(sel.id)) continue;

                local idName = (isDefined(sel.idName) && sel.idName != "") ? sel.idName : "empty";
                UIEffectDropDownMenu.setMenuToId(sel.id, idName, true); // fire callback
            }
        }

        // Restore FX parameters for the current fxchainScope, skipping selectors (already set)
        if (isDefined(params)) {
            for (i = 0; i < params.length; i++) {
                local p = params[i];
                if (!isDefined(p) || !isDefined(p.id)) continue;
                if (!_isFxParam(p.id)) continue;
                if (p.id.contains("EffectSelector")) continue; // handled above

                local c = Content.getComponent(p.id);
                if (!isDefined(c)) continue;

                c.setValue(p.value);
                c.changed();
            }
        }

And you can hopefully see, that what that is doing is skipping userPresetLoad altogether - and instead is manually iterating around whatever data exists in the file, finding the right UI component, and setting the value. This allows me to circumvent some of the HISE assumptions; namely that if a UI component is not specified when loading a user preset, it gets reset to the default value. Which is super no bueno.

Bear in mind some of this stuff can be asynchronous. So I don't think you can always rely on the order of things.

An approach could be to store an object in a panel that contains what you need like tags.
Then at init (or anytime you want really) you automatically create/update a unique JSON file that contains all the tags from all the available presets. So if a user shares a preset, this can be automated (or with a "collect tags from presets" button) and the local JSON file updates (as well as your preset browser which ever it is).

PS - did you see my latest email?