#summary List of gear-related functions in the Lua API

= Lua API: Gear functions =

<wiki:toc max_depth="3"/>

== Creation ==

=== `AddGear(x, y, gearType, state, dx, dy, timer)` ===

The initial velocities are `dx` and `dy`. All arguments are numbers. The function returns the `uid` of the gear created. Gears can have multple states at once: `state` is a bitmask, the flag variables can be found in [States].

Example:

<code language="lua">    local gear = AddGear(0, 0, gtTarget, 0, 0, 0, 0)

    FindPlace(gear, true, 0, LAND_WIDTH)</code>

=== `AddVisualGear(x, y, visualGearType, state, critical [, layer])` ===

The function returns the `uid` of the visual gear created or `nil` if creation failed.  There is no guarantee that a visual gear will spawn.  *IMPORTANT: Do not rely on visual gears to spawn*. *Always* be prepared for this function to return `nil`.

Set `critical` to `true` if the visual gear is crucial to gameplay and must always be spawned when in-game.  Use `false` if it is just an effect or eye-candy, and its creation can be skipped when in fast-forward mode (such as when joining a room).

You can set an optional `layer` to specify which visual gears get drawn on top.

Most visual gears delete themselves eventually.

*NOTE:* Visual gears *must* only be used for decorational/informational/rendering purposes. *Never* use the visual gear's internal state to manipulate anything gameplay-related. Visual gears are not safe for reliable storage and using them as that would lead to strange bugs.

*NOTE:* Since 0.9.25, visual gears will never spawn when Hedgewars is run in a testing mode (i.e. not as the real game), so don't rely for visual gears to spawn even if they're critical.

Example:

<code language="lua">  -- adds an non-critical explosion at position 1000,1000. Returns 0 if it was not created.

    local vgear = AddVisualGear(1000, 1000, vgtExplosion, 0, false) 

</code>

=== `AddHog(hogname, botlevel, health, hat)` ===

Adds a new hedgehog for current team (last created one with the `AddTeam` function), with a bot level, an initial health and a hat.

`botlevel` ranges from `0` to `5`, where `0` denotes a human player and `1` to `5` denote the skill level of a bot, where `1` is strongest and `5` is the weakest. Note that this is the reverse order of how the bot level is displayed in the game. Note that mixing human-controlled and computer-controlled hedgehogs in the same team is not permitted, but it is permitted to use different computer difficulty levels in the same team.

Returns the gear ID.

*Warning*: This only works in singleplayer mode (e.g. missions). Also, Hedgewars only supports up to 64 hedgehogs in a game.

Example:

<code language="lua">    local player = AddHog("HH 1", 0, 100, "NoHat") -- botlevel 0 means human player

    SetGearPosition(player, 1500, 1000)

    -- hint: If you don't call `SetGearPosition`, the hog spawns randomly</code>

=== `AddMissionHog(health)` (0.9.25) ===

Add a hedgehog for the current team, using the player-chosen team identity when playing in singleplayer missions. The “current team” is the last team that was added with `AddMissionTeam` or `AddTeam`.

The name and hat match the player's team definition. The hog is also always player-controlled.

Examples:

<code language="lua">-- Add player team with 3 hogs

AddMissionTeam(-1)

AddMissionHog(100)

AddMissionHog(100)

AddMissionHog(100)</code>

<code language="lua">-- You can also mix mission hogs with “hardcoded” hogs.

-- This adds a player team with 2 hogs taken from the player team and 1 hog with a hardcoded name, botlevel and hat.

AddMissionTeam(-2)

AddMissionHog(100)

AddMissionHog(100)

AddHog("My Hardcoded Hog", 0, 100, "NoHat")

</code>

=== `SpawnHealthCrate(x, y, [, health])` ===

Spawns a health crate at the specified position. If `x` and `y` are set to 0, the crate will spawn on a random position (but always on land). Set `health` for the initial health contained in the health crate. If not set, the default health (`HealthCaseAmount`) is used. Do not use a negative value for `health`.

=== `SpawnSupplyCrate(x, y, ammoType [, amount])` (0.9.24) ===

Spawns an ammo or utility crate at the specified position with the given ammo type and an optional amount (default: 1). The crate type is chosen automatically based on the ammo type.

Otherwise, this function behaves like `SpawnAmmoCrate`.

=== `SpawnAmmoCrate(x, y, ammoType [, amount])` ===

Spawns an ammo crate at the specified position with content of `ammoType` (see [AmmoTypes Ammo Types]). Any `ammoType` is permitted, an ammo crate is spawned even if the ammo is normally defined as an utility.

If `ammoType` is set to `amNothing`, a random weapon (out of the available weapons from the weapon scheme) will be selected. If `x` and `y` are set to 0, the crate will spawn on a random position (but always on land). The `amount` parameter specifies the amount of ammo contained in the crate. If `amount` is `nil` or `0`, the value set by `SetAmmo` is used, or if `SetAmmo` has not been used, it falls back to the weapon scheme's value. If `amount` is equal to or greater than `AMMO_INFINITE`, the amount is infinite.

Note that in Lua missions, the default number of ammo in crates is 0, so it has to be set to at least 1 with `SetAmmo` first, see the example:

Example:

<code language="lua">    SetAmmo(amGrenade, 0, 0, 0, 1) -- grenade ammo crates now contain 1 grenade each

    SpawnAmmoCrate(0, 0, amGrenade) -- spawn grenade ammo crate at random position</code>

=== `SpawnUtilityCrate(x, y, ammoType [, amount])` ===

Spawns an utility crate with some ammo at the specified position. The function behaves almost like `SpawnAmmoCrate`, the differences are 1) the crate looks different and 2) if `ammoType` is set to `amNothing`, a random utility out of the set of available utilities from the weapon scheme is chosen as content.

Example:

<code language="lua">    SetAmmo(amLaserSight, 0, 0, 0, 1)

    SpawnUtilityCrate(0, 0, amLaserSight)</code>

=== `SpawnFakeAmmoCrate(x, y, explode, poison) ` ===

Spawns a crate at the specified coordinates which looks exactly like a real ammo crate but contains not any ammo. It can be use useful for scripted events or to create a trap. If `x` and `y` are set to 0, the crate will spawn on a random position (but always on land).

`explode` and `poison` are booleans.

If `explode` is `true`, the crate will explode when collected.

If `poison` is `true`, the collector will be poisoned.

Example:

<code language="lua">SpawnFakeAmmoCrate(500, 432, false, false) -- Spawns a fake ammo crate at the coordinates (500, 434) without explosion and poison.

</code>

=== `SpawnFakeHealthCrate(x, y, explode, poison) ` ===

Same as `SpawnFakeAmmoCrate`, except the crate will look like a health crate.

=== `SpawnFakeUtilityCrate(x, y, explode, poison) ` ===

Same as `SpawnFakeAmmoCrate`, except the crate will look like an utility crate.

== Position and velocity ==

=== `GetGearPosition(gearUid)` ===

Returns x,y coordinates for the specified gear. Not to be confused with `GetGearPos`.

=== `GetX(gearUid)` ===

Returns x coordinate of the gear.

=== `GetY(gearUid)` ===

Returns y coordinate of the gear.

=== `SetGearPosition(gearUid, x, y)` ===

Places the specified gear exactly at the position (`x`,`y`). Not to be confused with `SetGearPos`.

=== `GetGearVelocity(gearUid)` ===

Returns a tuple of dx,dy values for the specified gear.

=== `SetGearVelocity(gearUid, dx, dy)` ===

Gives the specified gear the velocity of `dx`, `dy`.

=== `CopyPV(gearUid, gearUid)` ===

This sets the position and velocity of the second gear to the first one.

=== `FindPlace(gearUid, fall, left, right[, tryHarder])` ===

Finds a place for the specified gear between x=`left` and x=`right` and places it there. `tryHarder` is optional, setting it to `true`/`false` will determine whether the engine attempts to make additional passes, even attempting to place gears on top of each other.

Example:

<code language="lua">    gear = AddGear(...)

    FindPlace(gear, true, 0, LAND_WIDTH) -- places the gear randomly between 0 and LAND_WIDTH</code>

== General gear properties ==

=== `GetGearType(gearUid)` ===

This function returns the [GearTypes gear type] for the specified gear, if it exists.  If it doesn't exist, `nil` is returned.

=== `GetVisualGearType(vgUid)` (0.9.23) ===

This function returns the [VisualGearTypes visual gear type] for the specified visual gear, if it exists.  If it doesn't exist, `nil` is returned.

=== `GetState(gearUid)` ===

Returns the state of the gear. The gear state is a bitmask which is built out of the variables as shown in [States].

This function is usually used in combination with `band` to extract the truth value of a single flag. It is also used together with `SetState` and `bor` in order to activate a single flag.

Examples:

<code language="lua">

local state = GetState(gear)

--[[ Stores the full raw bitmask of gear in state. Usually

useless on its own. ]]

</code>

<code language="lua">

isDrowning = band(GetState(CurrentHedgehog),gstDrowning) ~= 0

--[[ GetState(CurrentHedgehog) returns the state bitmask of

CurrentHedgehog, gstDrowning is a bitmask where only the

“drowning” bit is set. band does a bitwise AND on both, if

it returns a non-zero value, the hedgehog is drowning.]]

</code>

<code language="lua">

SetState(CurrentHedgehog, bor(GetState(CurrentHedgehog), gstInvisible))

--[[ first the state bitmask of CurrentHedgehog is bitwise ORed with

the gstInvisible flag, thus making the bit responsible for

invisiblity to become 1. Then the new bitmask is applied to

CurrentHedgehog, thus making it invisible.]]

</code>

=== `SetState(gearUid, state)` ===

Sets the state of the specified gear to the specified `state`. This is a bitmask made out of the variables as seen in [States].

This function is often used together with `GetState` and the bitmask utility functions `band` and `bnot` in order to manipulate a single flag.

Examples:

<code language="lua">

SetState(CurrentHedgehog, bor(GetState(CurrentHedgehog), gstInvisible))

--[[ first the state bitmask of CurrentHedgehog is bitwise ORed with

the gstInvisible flag, thus making the bit responsible for

invisiblity to become 1. Then the new bitmask is applied to

CurrentHedgehog, thus making it invisible. ]]

</code>

<code language="lua">

SetState(CurrentHedgehog, band(GetState(CurrentHedgehog), bnot(gstInvisible)))

--[[ The reverse of the above: This function toggles CurrentHedgehog’s

gstInvisible flag off, thus making it visible again. ]]

</code>

=== `GetGearMessage(gearUid)` ===

Returns the message of the gear. This is a bitmask built out of flags seen in [GearMessages].

=== `SetGearMessage(gearUid, message)` ===

Sets the gear messages of the specified gear. `message` is a bitmask built out of flags seen in [GearMessages].

=== `GetTag(gearUid)` ===

Returns the tag of the specified gear (by `gearUid`). 

The `Tag` of a gear is just another arbitrary variable to hold the gear's state. The meaning of a tag depends on the gear type. For example, for `gtBall` gears, it specifies the ball color, for `gtAirAttack` gears (airplane) it specifies the direction of the plane, etc. See [GearTypes] for a full list. The returned value will be an integer.

Note that the word “tag” here does _not_ refer to the name and health tags you see above hedgehogs, this is something different. 

<code language="lua">

-- This adds a ball (the one from the ballgun) at (123, 456):

ball = AddGear(123, 456, gtBall, 0, 0, 0, 0)

-- The tag of a ball defines its color. It will automatically chosen at random when created.

colorTag = GetTag(ball)

-- Now colorTag stores the tag of ball (in this case a number denoting its color)

</code>

The meaning of tags are described in [GearTypes].

=== `SetTag(gearUid, tag)` ===

Sets the `Tag` value of the specified gear (by `gearUid`). The `Tag` value of a gear is simply an extra variable to modify misc. things. The meaning of a tag depends on the gear type. For example, for `gtBall` gears, it specifies the ball color, for `gtAirAttack` gears (airplane) it specifies the direction of the plane, etc. See [GearTypes] for a full list. `tag` has to be an integer.

Note that the word “tag” here does _not_ refer to the name and health tags you see above hedgehogs, this is something different. 

<code language="lua">

-- This adds a ball (the one from the ballgun) at (123, 456):

ball = AddGear(123, 456, gtBall, 0, 0, 0, 0)

-- This sets the tag of the gear. For gtBall, the tag specified the color. “8” is the color white.

SetTag(ball, 8) -- 

</code>

The meaning of tags are described in [GearTypes].

=== `GetTimer(gearUid)` ===

Returns the timer of the gear. This is for example the time it takes for watermelon, mine, etc. to explode. This is also the time used to specify the blowtorch or RC plane time. See [GearTypes] for a full list.

=== `SetTimer(gearUid, timer)` ===

Sets the timer of the specified gear. Also see `GetTimer`.

=== `GetHealth(gearUid)` ===

Returns the health of the gear. Depending on the gear type, the gear's “health” can also refer to other things, see [GearTypes] for a full list.

=== `SetHealth(gearUid, health)` ===

Sets the health of the specified gear. The “health” of a gear can refer to many things, depending on the gear type.

*Hint*: If you like to increase the health of a hedgehog with nice visual effects, consider using `HealHog` instead.

Use cases:

  * Setting the health of a hedgehog (`gtHedgehog`) to 99

  * Starting the RC Plane (`gtRCPlane`) with 10 bombs

  * Starting flying saucer (`gtJetpack`) with only 50% fuel

  * Setting all the mines (`gtMine`) to duds

  * And more!

See [GearTypes] for a full description.

<code language="lua">    function onGearAdd(gear)

       if (GetGearType(gear) == gtHedgehog) then

            -- Set hedgehog health to 99

            SetHealth(gear, 99)

       end

       if (GetGearType(gear) == gtRCPlaane) then

            -- Give the plane 10 bombs

            SetHealth(gear, 10)

       end

       if (GetGearType(gear) == gtJetpack) then

            -- Set fuel to 50% only

            SetHealth(gear, 1000)

       end

       if (GetGearType(gear) == gtMine) then

            -- Turn mine into dud

            SetHealth(gear, 0)

       end

    end</code>

=== `GetGearPos(gearUid)` ===

Get the `Pos` value of the specified gear. `Pos` is just another arbitrary value to hold the state of the gear, such as `Tag` and `Health`, the meaning depends on the gear type. See [GearTypes] for the conrete meaning of a gear's `Pos` value. 

*Important*: Pos is *not* related to the gear's position, use `GetGearPosition` for that.

=== `SetGearPos(gearUid, value)` ===

Sets the `Pos` value (not the position!) of the specified gear to specified value. See `GetGearPos` for more information.

=== `GetGearCollisionMask(gearUid)` ===

Returns the current collision mask of the given gear. See `SetGearCollisionMask` for an explanation of the mask.

=== `SetGearCollisionMask(gearUid, mask)` ===

Set the collision mask of the given gear with `gearUid`.

The collision mask defines with which gears and terrain types the gear can collide.

`mask` is a number between `0x0000` and `0xFFFF` and used as a bitfield, which means you can combine these flags with `bor`. These are the available flags:

|| *Identifier* || *Collision with …* ||

|| `lfLandMask` || Terrain ||

|| `lfCurHogCrate` || Current hedgehog, and crates ||

|| `lfHHMask` || Any hedgehogs ||

|| `lfNotHHObjMask` || Objects, not hogs (e.g. mines, explosives) ||

|| `lfAllObjMask` || Hedgehogs and objects ||

Beware, the collision mask is often set by the engine as well.

Examples:

<code language="lua">SetGearCollisionMask(gear, bnot(lfCurHogCrate))

-- Ignore collision with current hedgehog</code>

<code language="lua">SetGearCollisionMask(gear, 0xFFFF)

-- Collide with everything</code>

<code language="lua">SetGearCollisionMask(gear, lfAllObjMask)

-- Collide with hedgehogs and objects</code>

<code language="lua">SetGearCollisionMask(gear, 0x0000)

-- Collide with nothing</code>

There are actual more flags availbable, but they are not as useful for use in Lua and their constants have not been exposed to Lua. You can find the full range of flags in the engine source code (in Pascal):

[https://hg.hedgewars.org/hedgewars/file/default/hedgewars/uConsts.pas#l112]

=== `GetGearRadius(gearUid)` ===

Returns the `Radius` value for the specified gear. For most [GearTypes gear types] for “projectile” gears (like `gtShell` or `gtGrenade`), the radius refers to the gear's collision radius. This is an invisible circle around the center of the gear which is used for the collision checks. For a few gear types, its radius means something different, see [GearTypes] for a full list.

To set the `Radius` value, use `SetGearValues`.

=== `GetFlightTime(gearUid)` ===

Returns the `FlightTime` of the specified gear. The `FlightTime` is a gear varialbe used to store a general time interval. The precise meaning of the `FlightTime` depends on the gear type.

For example: The `FlightTime` of a hedgehog (`gtHedgehog`) is the time since they last have stood on solid ground. For most projectile gear types (i.e. `gtShell`), it stores the time after it has been launched.

=== `SetFlightTime(gearUid, flighttime)` ===

Sets the `FlightTime` of the given gear to `flighttime`. The meaning of `FlightTime` is explained in the section `GetFlightTime`.

=== `GetGearElasticity(gearUid) ` ===

Returns the elasticity of the specified gear. The elasticity normally determines how strong the gear will bounce after collisions, where higher elasticity is for stronger bounces.

This is also useful for determining if a hog is on a rope or not. If a hog is attached to a rope, or is busy firing one, the elasticity of the rope will be a non-zero number.

=== `SetGearElasticity(gearUid, Elasticity) ` ===

Sets the elasticity of the specified gear. For most gears, the elasticity determines how strong the gear will bounce after collisions, where higher elasticity is for stronger bounces. Recommended are values between `0` and `9999`.

=== `GetGearFriction(gearUid) ` ===

Returns the friction of the specified gear. The friction normally determines how well the gear will slide on terrain. Higher values are for increased sliding properties.

=== `SetGearFriction(gearUid, Friction) ` ===

Sets the friction of the specified gear. The friction normally determines how well the gear will slide on terrain. Higher values are for increased sliding properties. `0` is for no sliding whatsoever, where `9999` is for very long slides, greater values are not recommended.

=== `GetGearTarget(gearUid, x, y) ` ===

Returns the x and y coordinate of target-based weapons/utilities. 

<b>Note:</b>: This can’t be used in `onGearAdd()` but must be called after gear creation. 

=== `SetGearTarget(gearUid, x, y)` ===

Sets the x and y coordinate of target-based weapons/utilities.

*Note*: This can’t be used in onGearAdd() but must be called after gear creation.

=== `GetGearValues(gearUid)` ===

This returns a bunch of values associated with the gear, their meaning is often depending on the gear type and many values might be unused for certain gear types.

This is returned (all variables are integers):

`Angle, Power, WDTimer, Radius, Density, Karma, DirAngle, AdvBounce, ImpactSound, nImpactSounds, Tint, Damage, Boom`

A rough description of some of the parameters:

 * `Radius`: Effect or collision radius, most of the time

 * `ImpactSound`: Sound it makes on a collision (see [Sounds])

 * `Tint`: Used by some gear types to determine its colorization. The color is in RGBA format.

 * `Boom`: Used by most gears to determine the damage dealt.

Example:

<code language="lua">

-- Get all values in a single line of code:

local Angle, Power, WDTimer, Radius, Density, Karma, DirAngle, AdvBounce, ImpactSound, nImpactSounds, Tint, Damage, Boom, Scale = GetGearValues(myGear)

</code>

=== `SetGearValues(gearUid, Angle, Power, WDTimer, Radius, Density, Karma, DirAngle, AdvBounce, ImpactSound, ImpactSounds, Tint, Damage, Boom)` ===

Sets various gear value for the specified gear (`gearUid`). The meaining of each value often depends on the gear type. See the documentation on !GetGearValues for a brief description of the gear values. If `gearUid` is invalid or the gear does not exist, nothing happens.

Set `nil` for each value you do not want to change.

Example:

<code language="lua">

-- Paints all RC planes into a white color

function onGearAdd(gear)

    if GetGearType(gear) == gtRCPlane then

         SetGearValues(gear, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, 0xFFFFFFFF)

    end

end

</code>

=== `GetVisualGearValues(vgUid)` ===

This returns the typically set visual gear values for the specified visual gear `vgUid`, useful if manipulating things like smoke, bubbles or circles. On success, it returns the following values:

`X, Y, dX, dY, Angle, Frame, FrameTicks, State, Timer, Tint, Scale`

The meaning of these values is the same as in `SetVisualGearValues`.

If the visual gear does not exist, `nil` is returned. Always check the result for `nil` before you plug in the values anywhere.

Most visual gears require little to no modification of parameters.

Example:

<code language="lua">-- Return visual gear values

local X, Y, dX, dY, Angle, Frame, FrameTicks, State, Timer, Tint, Scale = GetVisualGearValues(vgUid)

</code>

=== `SetVisualGearValues(vgUid, X, Y, dX, dY, Angle, Frame, !FrameTicks, State, Timer, Tint, Scale)` ===

This allows manipulation of the internal state of the visual gear `vgUid`. If `vgUid` is invalid or the `vgUid` does not refer to an existing visual gear, the function does nothing. Thus, you can safely call this function even if you are not sure if the visual gear actually exists.

All visual gear values are numbers. Each visual gear may be using these parameters differently, but the *usual* meaning of these is the following:

 * `X`, `Y`: Position

 * `dX`, `dY`: Speed along the X and Y axis

 * `Angle`: Current rotation

 * `Frame`: Image frame, if using a sprite sheet

 * `FrameTicks` is usually an animation counter

 * `State`: Helper value to save some internal state

 * `Timer`: Time in milliseconds until it expires

 * `Tint`: RGBA color

 * `Scale` is a scale factor (not used by all visual gears)

Some visual gears interpret these values differently, just like normal gears. See [VisualGearTypes] for details.  Also, most visual gears are not using all possible values, while some values are just ignored.

Note that most visual gears require little to no modification of their values.

*NOTE*: *Never* use the visual gear's internal state to manipulate/store anything gameplay-related.  Visual gears are not safe for reliable storage and using them as that would lead to strange bugs.

Example 1:

<code language="lua">  -- set a circle to position 1000,1000 pulsing from opacity 20 to 200 (8%-78%), radius of 50, 3px thickness, bright red.

    SetVisualGearValues(circleUid, 1000,1000, 20, 200, 0, 0, 100, 50, 3, 0xff0000ff)</code>

Only the first argument is required. Everything else is optional. Any such argument which is declared as `nil` will not overwrite the corresponding value of the visual gear.

Example 2:

<code language="lua">  -- set a visual gear to position 1000,1000

    SetVisualGearValues(circleUid, 1000, 1000)</code>

<code language="lua">  -- set the tint of a visual gear to bright red.

    SetVisualGearValues(circleUid, nil, nil, nil, nil, nil, nil, nil, nil, nil, 0xff0000ff)</code>

=== `SetGearAIHints(gearUid, aiHint)` ===

Set some behaviour hints for computer-controlled hedgehogs for any given gear with `gearUid`.

Set `aiHint` to either of:

 * `aihUsualProcessing`: AI hogs treat this gear the usual way. This is the default.

 * `aihDoesntMatter`: AI hogs don't bother attacking this gear intentionally.

Example:

<code language="lua">

SetGearAIHints(uselessHog, aihDoesntMatter)

-- This makes AI hogs stop caring about attacking uselessHog</code>

== Hedgehog-specific gear properties ==

=== `GetHogName(gearUid)` ===

Returns the name of the specified hedgehog gear.

=== `SetHogName(gearUid, name)` ===

Sets the name of the specified hedgehog gear.

=== `GetHogTeamName(gearUid)` ===

Returns the name of the specified gear’s team. `gearUid` can be a hedgehog or a grave.

=== `SetHogTeamName(gearUid, name)` ===

Sets the team name of the specified gear. The gear can be a hedgehog or grave.

=== `GetHogClan(gearUid)` ===

Returns the clan ID of the specified hedgehog gear.

=== `GetHogLevel(gearUid)` ===

Returns the bot level ranging from `0` to `5`. `1` is the strongest bot level and `5` is the weakest one (this is the reverse of what players see). `0` is for human player.

=== `SetHogLevel(gearUid, level)` ===

Sets the bot level from 0 to 5. `1` is the strongest bot level and `5` is the weakest one (this is the reverse of what players see). `0` means human player.

=== `GetEffect(gearUid, effect)` ===

Returns the state of given effect for the given hedgehog gear.